Democracy is a form of government in which political power is vested in the people or the population of a state. Under a minimalist definition of democracy, rulers are elected through competitive elections while more expansive or maximalist definitions link democracy to guarantees of civil liberties and human rights in addition to competitive elections.
In a direct democracy, the people have the direct authority to deliberate and decide legislation. In a representative democracy, the people choose governing officials through elections to do so. The definition of "the people" and the ways authority is shared among them or delegated by them have changed over time and at varying rates in different countries. Features of democracy often include freedom of assembly, association, personal property, freedom of religion and speech, citizenship, consent of the governed, voting rights, freedom from unwarranted governmental deprivation of the right to life and liberty, and minority rights.
The notion of democracy has evolved considerably over time. Throughout history, one can find evidence of direct democracy, in which communities make decisions through popular assembly. Today, the dominant form of democracy is representative democracy, where citizens elect government officials to govern on their behalf such as in a parliamentary or presidential democracy. In the common variant of liberal democracy, the powers of the majority are exercised within the framework of a representative democracy, but a constitution and supreme court limit the majority and protect the minority—usually through securing the enjoyment by all of certain individual rights, such as freedom of speech or freedom of association.
The term appeared in the 5th century BC in Greek city-states, notably Classical Athens, to mean "rule of the people", in contrast to aristocracy (ἀριστοκρατία, aristokratía), meaning "rule of an elite". In virtually all democratic governments throughout ancient and modern history, democratic citizenship was initially restricted to an elite class, which was later extended to all adult citizens. In most modern democracies, this was achieved through the suffrage movements of the 19th and 20th centuries.
Democracy contrasts with forms of government where power is not vested in the general population of a state, such as authoritarian systems. Historically a rare and vulnerable form of government, democratic systems of government have become more prevalent since the 19th century, in particular with various waves of democratization. Democracy garners considerable legitimacy in the modern world, as public opinion across regions tends to strongly favor democratic systems of government relative to alternatives, and as even authoritarian states try to present themselves as democratic. Democracy more consistently results in improved health, education and economic outcomes. According to the V-Dem Democracy indices and The Economist Democracy Index, less than half the world's population lives in a democracy as of 2022. At the same time, while representative democracy is widely valued, Pew Research Center found that dissatisfaction with democratic performance is common even in many established democracies.

== Characteristics ==

In purely representative democracies, democracy is understood to be defined by free voting. No consensus exists on a precise definition of democracy
(see also In the search of common understanding below),
and many approaches have been taken to define it. A study identified 2,234 adjectives used to describe democracy in the English language.
Yet, there is a profound understanding of its meaning – like that of Abraham Lincoln:

"Government of the people, by the people, for the people"
or of Karl Popper saying that the "classical" view of democracy is, "in brief, the theory that:

democracy is the rule of the people and that the people have a right to rule.
Democratic principles are reflected in all eligible citizens being equal before the law and having equal access to legislative processes, even if not every vote cast elects someone.
For example, in a representative democracy, every vote has (in theory) equal weight, and the freedom of eligible citizens is secured by legitimised rights and liberties which are typically enshrined in a constitution, while other uses of "democracy" may encompass direct democracy, in which citizens vote on issues directly. According to the United Nations, democracy "provides an environment that respects human rights and fundamental freedoms, and in which the freely expressed will of people is exercised."
One theory holds that democracy requires three fundamental principles: upward control (sovereignty residing at the lowest levels of authority), political equality, and social norms by which individuals and institutions only consider acceptable acts that reflect the first two principles of upward control and political equality. Legal equality, political freedom and rule of law are often identified by commentators as foundational characteristics for a well-functioning democracy.
In some countries, notably in the United Kingdom (which originated the Westminster system), the dominant principle is that of parliamentary sovereignty, while maintaining judicial independence. In India, parliamentary sovereignty is subject to the Constitution of India which includes judicial review. Though the term "democracy" is typically used in the context of a political state, the principles also are potentially applicable to private organisations, such as clubs, societies and firms.
Democracies may use many different decision-making methods, but majority rule is the dominant form. Without compensation, like legal protections of individual or group rights, political minorities can be oppressed by the "tyranny of the majority". Majority rule involves a competitive approach, opposed to consensus democracy, creating the need that elections, and generally deliberation, be substantively and procedurally "fair", i.e., just and equitable. In some countries, freedom of political expression, freedom of speech, and freedom of the press are considered important to ensure that voters are well informed, enabling them to vote according to their own interests and beliefs.
It has also been suggested that a basic feature of democracy is the capacity of all voters to participate freely and fully in the life of their society. With its emphasis on notions of social contract and the collective will of all the voters, democracy can also be characterised as a form of political collectivism because it is defined as a form of government in which all eligible citizens have an equal say in lawmaking.
Republics, though often popularly associated with democracy because of the shared principle of rule by consent of the governed, are not necessarily democracies, as republicanism does not specify how the people are to rule. Classically the term "republic" encompassed both democracies and aristocracies and their mixtures. In a modern sense the republican form of government is a form of government without a monarch. Because of this, democracies can be republics or constitutional monarchies, such as the United Kingdom, where the monarch is not a ruler.

== History ==

Democratic assemblies are as old as the human species and are found throughout human history, but up until the nineteenth century, major political figures have largely opposed democracy. Republican theorists linked democracy to small size: as political units grew in size, the likelihood increased that the government would turn despotic. At the same time, small political units were vulnerable to conquest. Montesquieu wrote, "If a republic be small, it is destroyed by a foreign force; if it is large, it is ruined by an internal imperfection." According to Johns Hopkins University political scientist Daniel Deudney, the creation of the United States, with its large size and its system of checks and balances, was a soluti


Human rights are universally recognized moral principles or norms that establish standards of human behavior and are often protected by both national and international laws. These rights are considered inherent and inalienable, meaning they belong to every individual simply by virtue of being human. They encompass a broad range of civil, political, economic, social, and cultural rights, such as the right to life, freedom of speech, protection against enslavement, and right to education.
While ideas related to human rights predate modernity, the modern concept of human rights gained significant prominence after World War II, particularly in response to the atrocities of the Holocaust, leading to the adoption of the Universal Declaration of Human Rights (UDHR) by the United Nations General Assembly in 1948. This document outlined a comprehensive framework of rights that countries are encouraged to protect, setting a global standard for human dignity, freedom, and justice. The Universal Declaration of Human Rights (UDHR) has since inspired numerous international treaties and national laws aimed at promoting and protecting human rights worldwide.
While the principle of universal human rights is widely accepted, debates persist regarding which rights should take precedence, how they should be implemented, and their applicability in different cultural contexts. Criticisms often arise from perspectives like cultural relativism, which argue that individual human rights are inappropriate for societies that prioritize a communal or collectivist identity, and may conflict with certain cultural or traditional practices.
Nonetheless, human rights remain a central focus in international relations and legal frameworks, supported by institutions such as the United Nations, various non-governmental organizations, and national bodies dedicated to monitoring and enforcing human rights standards worldwide.

== History ==

Many of the basic ideas that animated the human rights movement developed in the aftermath of the Second World War and the events of the Holocaust, culminated in the adoption of the Universal Declaration of Human Rights in Paris by the United Nations General Assembly in 1948.
Ancient peoples did not have the same modern-day conception of universal human rights. However, the concept has in some sense existed for centuries, although not in the same way as today. In the West, Jewish and Christian scriptures provided some conceptual foundations for discourse on rights along with Roman law providing legal foundations on what implementation may look like.
The true forerunner of human rights discourse was the concept of natural rights, which first appeared as part of the medieval natural law tradition. It developed in new directions during the European Enlightenment with such philosophers as John Locke, Francis Hutcheson, and Jean-Jacques Burlamaqui, and featured prominently in the political discourse of the American Revolution and the French Revolution. From this foundation, the modern human rights arguments emerged over the latter half of the 20th century, possibly as a reaction to slavery, torture, genocide, and war crimes.
The medieval natural law tradition was heavily influenced by the writings of St Paul's early Christian thinkers such as St Hilary of Poitiers, St Ambrose, and St Augustine. Augustine was among the earliest to examine the legitimacy of the laws of man, and attempt to define the boundaries of what laws and rights occur naturally based on wisdom and conscience, instead of being arbitrarily imposed by mortals, and if people are obligated to obey laws that are unjust.
The Kouroukan Fouga was the constitution of the Mali Empire in West Africa. It was composed in the 13th century, and was one of the very first charters on human rights. It included the "right to life and to the preservation of physical integrity" and significant protections for women.
Spanish scholasticism insisted on a subjective vision of law during the 16th and 17th centuries: Luis de Molina, Domingo de Soto and Francisco Vitoria, members of the School of Salamanca, defined law as a moral power over one's own. Although they maintained at the same time, the idea of law as an objective order, they stated that there are certain natural rights, mentioning both rights related to the body (right to life, to property) and to the spirit (right to freedom of thought, dignity). The jurist Vázquez de Menchaca, starting from an individualist philosophy, was decisive in the dissemination of the term iura naturalia. This natural law thinking was supported by contact with American civilizations and the debate that took place in Castile about the just titles of the conquest and, in particular, the nature of the indigenous people. In the Castilian colonization of America, it is often stated, measures were applied in which the germs of the idea of Human Rights are present, debated in the well-known Valladolid Debate that took place in 1550 and 1551. The thought of the School of Salamanca, especially through Francisco Vitoria, also contributed to the promotion of European natural law.
From this foundation, the modern human rights arguments emerged over the latter half of the 20th century. Magna Carta is an English charter originally issued in 1215 which influenced the development of the common law and many later constitutional documents related to human rights, such as the 1689 English Bill of Rights, the 1789 United States Constitution, and the 1791 United States Bill of Rights.
17th century English philosopher John Locke discussed natural rights in his work, identifying them as being "life, liberty, and estate (property)", and argued that such fundamental rights could not be surrendered in the social contract. In Britain in 1689, the English Bill of Rights and the Scottish Claim of Right each made a range of oppressive governmental actions, illegal. Two major revolutions occurred during the 18th century, in the United States (1776) and in France (1789), leading to the United States Declaration of Independence and the French Declaration of the Rights of Man and of the Citizen respectively, both of which articulated certain human rights. Additionally, the Virginia Declaration of Rights of 1776 encoded into law a number of fundamental civil rights and civil freedoms.

We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.

=== 1800 to World War I ===

Philosophers such as Thomas Paine, John Stuart Mill, and Hegel expanded on the theme of universality during the 18th and 19th centuries. In 1831, William Lloyd Garrison wrote in a newspaper called The Liberator that he was trying to enlist his readers in "the great cause of human rights", so the term human rights probably came into use sometime between Paine's The Rights of Man and Garrison's publication. In 1849 a contemporary, Henry David Thoreau, wrote about human rights in his treatise On the Duty of Civil Disobedience which was later influential on human rights and civil rights thinkers. United States Supreme Court Justice David Davis, in his 1867 opinion for Ex Parte Milligan, wrote "By the protection of the law, human rights are secured; withdraw that protection and they are at the mercy of wicked rulers or the clamor of an excited people."
Many groups and movements have managed to achieve profound social changes over the course of the 20th century in the name of human rights. In Western Europe and North America, labour unions brought about laws granting workers the right to strike, establishing minimum work conditions and forbidding or regulating child labour. The women's rights movement succeeded in gaining for many women the right to vote. National liberation movements in many countries succeeded in driving out colonial powers. One of the most influential was Mahatma Gandhi's leade


Medicine is the science and practice of caring for patients, managing the diagnosis, prognosis, prevention, treatment and palliation of their injury or disease, while promoting their health. Medicine encompasses a variety of health care practices which evolved to maintain and restore health through the prevention and treatment of illness and infection. Contemporary medicine applies biomedical sciences, biomedical research, genetics, and medical technology to diagnose, treat, and prevent injury and disease, typically through various pharmaceuticals or surgery, but also through therapies such as psychotherapy, external splints and traction, medical devices, biologics, and ionizing radiation, amongst others.
Medicine has been practiced since prehistoric times, and for most of this time it was an art (an area of creativity and skill), frequently having connections to the religious and philosophical beliefs of local culture. For example, a medicine man would apply herbs and say prayers for healing, or an ancient philosopher and physician would apply bloodletting according to the theories of humorism, or the four humors. In recent centuries, since the advent of modern science, most medicine has become a combination of art and science (both basic and applied, under the umbrella of medical science). For example, while stitching technique for sutures is an art learned through practice, science provides knowledge of what happens at the cellular and molecular level in the tissues being stitched.
Prescientific forms of medicine, now known as traditional medicine or folk medicine, remain commonly used in the absence of scientific medicine and are thus called alternative medicine. Alternative treatments outside of scientific medicine with ethical, safety and efficacy concerns are termed quackery or being based on fringe science.

== Etymology ==
Medicine (UK:  , US:  ) is the science and practice of the diagnosis, prognosis, treatment, and prevention of disease. The word "medicine" is derived from Latin medicus, meaning "a physician". The word "physic" itself, from which "physician" derives, was the old word for what is now called a medicine, and also the field of medicine.

== Clinical practice ==

Medical availability and clinical practice vary across the world due to regional differences in culture and technology. Modern scientific medicine is highly developed and widespread in the Western world, whereas in some low-resource regions—including parts of Africa, the Pacific Islands of Oceania, Southeast Asia, and Latin America—populations often rely more heavily on traditional medicine. These practices consist of decentralized training structures and vary widely in empirical support; consequently, they may lack formal regulatory oversight or robust evidence for clinical efficacy.
In the developed world, evidence-based medicine (EBM) is not universally applied in clinical practice; for example, a 2007 survey of literature reviews found that about 49% of medical interventions lacked sufficient evidence to support either benefit or harm. However, medical practitioners who apply an intervention with uncertain efficacy without adequate justification, transparency, or patient consent may violate the bioethical principle of non-maleficence, a core tenet of biomedical ethics historically associated with the Hippocratic Oath, which emphasizes a primary duty to "first, do no harm."
In modern clinical practice, physicians and mid-level practitioners such as physician assistants personally assess patients to diagnose, prognose, treat, and prevent disease using clinical judgment. An initial medical encounter with a patient typically begins with a review of the patient's medical history and medical record, followed by a medical interview and a physical examination. Basic diagnostic medical devices (e.g., stethoscope, tongue depressor) are typically used. After examining for signs and interviewing for symptoms, the doctor may order medical tests (e.g., blood tests), take a biopsy, or prescribe pharmaceutical drugs or other therapies. Differential diagnosis methods help to rule out conditions based on the information provided. During the encounter, properly informing the patient of all relevant facts is an important part of the relationship and the development of trust within the context of the doctor-patient relationship. The medical encounter is then documented in the medical record, which is a legal document in many jurisdictions. Follow-up encounters may be shorter but follow the same general procedure, and specialists follow a similar process. The diagnosis and treatment may take only a few minutes or a few weeks, depending on the complexity of the issue.
The components of the medical interview and encounter are:

Chief complaint (CC): the reason for the current medical visit. These are the symptoms. They are in the patient's own words and are recorded along with the duration of each one. Also called chief concern or presenting complaint.
Current activity: occupation, hobbies, what the patient actually does professionally and non-professionally.
Family history (FH): listing of diseases in the family that may impact the patient. A family tree is sometimes used.
History of present illness (HPI): the chronological order of events of symptoms and further clarification of each symptom. Distinguishable from history of previous illness, often called past medical history (PMH). Medical history comprises HPI and PMH.
Medications (Rx): what drugs the patient takes including prescribed, over-the-counter, and home remedies, as well as alternative and herbal medicines or remedies. Allergies are also recorded.
Past medical history (PMH/PMHx): concurrent medical problems, past hospitalizations and operations, injuries, past infectious diseases or vaccinations, history of known allergies.
Review of systems (ROS) or systems inquiry: a set of additional questions to ask, which may be missed on HPI: a general enquiry (have you noticed any weight loss, change in sleep quality, fevers, lumps and bumps? etc.), followed by questions on the body's main organ systems (heart, lungs, digestive tract, urinary tract, etc.).
Social history (SH): birthplace, residences, marital history, social and economic status, habits (including diet, medications, tobacco, alcohol).
The physical examination is the examination of the patient for medical signs of disease that are objective and observable, in contrast to symptoms that are volunteered by the patient and are not necessarily objectively observable. The healthcare provider uses sight, hearing, touch, and sometimes smell (e.g., in infection, uremia, diabetic ketoacidosis). Four actions are the basis of physical examination: inspection, palpation (feel), percussion (tap to determine resonance characteristics), and auscultation (listen), generally in that order, although auscultation occurs prior to percussion and palpation for abdominal assessments.
The clinical examination involves the study of:

Abdomen and rectum
Cardiovascular (heart and blood vessels)
General appearance of the patient and specific indicators of disease (nutritional status, presence of jaundice, pallor or clubbing)
Genitalia (and pregnancy if the patient is or could be pregnant)
Head, eye, ear, nose, and throat (HEENT)
Musculoskeletal (including spine and extremities)
Neurological (consciousness, awareness, brain, vision, cranial nerves, spinal cord and peripheral nerves)
Psychiatric (orientation, mental state, mood, evidence of abnormal perception or thought).
Respiratory (large airways and lungs)
Skin
Vital signs including height, weight, body temperature, blood pressure, pulse, respiration rate, and hemoglobin oxygen saturation
It is to likely focus on areas of interest highlighted in the medical history and may not include everything listed above.
The treatment plan may include ordering additional medical laboratory tests and medical imaging studies, starting therapy, referral to a


Surgery is a medical specialty that uses manual and instrumental techniques to diagnose or treat pathological conditions (e.g., trauma, disease, injury, malignancy), to alter bodily functions (e.g., malabsorption created by bariatric surgery such as gastric bypass), to reconstruct or alter aesthetics and appearance (cosmetic surgery), or to remove unwanted tissues, neoplasms and foreign bodies.
The act of performing surgery may be called a surgical procedure or surgical operation, or simply "surgery" or "operation". In this context, the verb "operate" means to perform surgery. The adjective surgical means pertaining to surgery; e.g. surgical instruments, surgical facility or surgical nurse. Most surgical procedures are performed by a pair of operators: a surgeon who is the main operator performing the surgery, and a surgical assistant who provides in-procedure manual assistance during surgery. Modern surgical operations typically require a surgical team that typically consists of the surgeon, the surgical assistant, an anaesthetist (often also complemented by an anaesthetic nurse), a scrub nurse (who handles sterile equipment), a circulating nurse and a surgical technologist, while procedures that mandate cardiopulmonary bypass will also have a perfusionist. All surgical procedures are considered invasive and often require a period of postoperative care (sometimes intensive care) for the patient to recover from the iatrogenic trauma inflicted by the procedure. The duration of surgery can span from several minutes to tens of hours depending on the specialty, the nature of the condition, the target body parts involved and the circumstance of each procedure, but most surgeries are designed to be one-off interventions that are typically not intended as an ongoing or repeated type of treatment.
In British colloquialism, the term "surgery" can also refer to the facility where surgery is performed, or simply the office/clinic of a physician, dentist or veterinarian.

== Definitions ==

As a general rule, a procedure is considered surgical when it involves cutting a person's tissues to treat a disease or injury. Other procedures that do not necessarily fall under this rubric, such as angioplasty or endoscopy, may be considered surgery if they involve "common" surgical procedure or settings, such as use of antiseptic measures and sterile fields, sedation/anesthesia, proactive hemostasis, typical surgical instruments, suturing or stapling. Minimally invasive surgeries are procedures that utilize natural orifices (e.g. most urological procedures), do not penetrate the structure being excised (e.g. endoscopic polyp excision, rubber band ligation, laser eye surgery), or are percutaneous (e.g. arthroscopy, catheter ablation, angioplasty and valvuloplasty).

=== Types of surgery ===
Surgical procedures are commonly categorized by urgency, type of procedure, body system involved, the degree of invasiveness, and special instrumentation.
Based on timing:
Elective surgery is done to correct a non-life-threatening condition, and is carried out at the person's convenience, or to the surgeon's and the surgical facility's availability.
Emergency surgery is surgery which must be done without any delay to prevent death or serious disabilities or loss of limbs and functions.
Urgent surgery is one that is better done early to avoid complications or potential deterioration of the patient's condition, but such risks are sufficiently low that the procedure can be postponed for a short period time.
Based on purpose:
Bariatric surgery is done to assist weight loss when dietary and pharmaceutical methods alone have failed.
Exploratory surgery is performed to establish or aid a diagnosis.
Non-survival surgery, or terminal surgery, is where euthanasia is performed while the subject is under anesthesia so that the subject will not regain conscious pain perception. This type of surgery is usually done in animal testing experiments.
Plastic surgery is done to improve a body part's function or appearance.
Cosmetic surgery is done to subjectively improve the appearance of an otherwise normal body part.
Reconstructive surgery is done to improve the function or subjective appearance of a damaged or malformed body part.
Therapeutic surgery is performed to treat a previously diagnosed condition.
Curative surgery is a therapeutic procedure done to permanently remove a pathology.
By type of procedure:
Ablation is destruction of tissue through the use of energy-transmitting devices such as electrocautery/fulguration, laser, focused ultrasound or freezing.
Amputation involves removing an entire body part, usually a limb or digit; castration is the amputation of testes; circumcision is the removal of prepuce from the penis or clitoral hood from the clitoris (see female circumcision). Replantation involves reattaching a severed body part.
Bypass involves the relocation/grafting of a tubular structure onto another in order to reroute the content flow of that target structure from a specific segment directly to a more distal ("downstream") segment.
Extirpation is the complete excision or surgical destruction of a body part.
Grafting is the relocation and establishment of a tissue from one part of the body to another. A flap is the relocation of a tissue without complete separation of its original attachment, and a free flap is a completely detached flap that carries an intact neurovascular structure ready for grafting onto a new location.
Implantation is insertion of artificial medical devices to replace or augment existing tissue.
Repair involves the direct closure or restoration of an injured, mutilated or deformed organ or body part, usually by suturing or internal fixation. Reconstruction is an extensive repair of a complex body part (such as joints), often with some degrees of structural/functional replacement and commonly involves grafting and/or use of implants.
Resection is the removal of all or part of an internal organ and/or connective tissue. A segmental resection specifically removes an independent vascular region of an organ such as a hepatic segment, a bronchopulmonary segment or a renal lobe. Excision is the resection of only part of an organ, tissue or other body part (e.g. skin) without discriminating specific vascular territories. Exenteration is the complete removal of all organs and soft tissue content (especially lymphoid tissues) within a body cavity.
Transplantation is the replacement of an organ or body part by insertion of another from a different human (or animal) into the person undergoing surgery. Harvesting is the resection of an organ or body part from a live human or animal (known as the donor) for transplantation into another patient (known as the recipient).
By organ system: Surgical specialties are traditionally and academically categorized by the organ, organ system or body region involved. Examples include:
Cardiac surgery — the heart and mediastinal great vessels;
ENT surgery — ear, nose and throat, also known as head and neck surgery when including the neck region;
Gastrointestinal surgery — the digestive tract and its accessory organs;
Neurosurgery — the central nervous system, and;
Oral and maxillofacial surgery — the oral cavity, jaws, and face;
Orthopedic surgery — the musculoskeletal system.
Thoracic surgery — the thoracic cavity including the lungs;
Urological surgery — the genitourinary system;
Vascular surgery — the extra-mediastinal great vessels and peripheral circulatory system;
By degree of invasiveness of surgical procedures:
Conventional open surgery (such as a laparotomy) requires a large incision to access the area of interest, and directly exposes the internal body cavity to the outside.
Hybrid surgery uses a combination of open and minimally-invasive techniques, and may include hand ports or larger incisions to assist with performance of elements of the procedure.
Minimally-invasive surgery involves much smaller surface incisions or even nat


Pharmacology is the science of drugs and medications, including a substance's origin, composition and interaction with biological systems; specifically through pharmacokinetics, pharmacodynamics, therapeutic use, and toxicology. The discipline examines these interactions through pharmacokinetics (what the body does to the drug) and pharmacodynamics (what the drug does to the body), both of which determine how a substance alters normal or abnormal biochemical function. Substances with medicinal properties are classified as pharmaceuticals, while the term drug encompasses any chemical agent that alters biological processes. Nanopharmacology is the specialization of pharmacology in the nanoscale.
The field encompasses drug composition and properties, functions, sources, medicinal chemistry, drug design, molecular and cellular mechanisms, organ/systems mechanisms, signal transduction/cellular communication, molecular diagnostics, interactions, chemical biology, therapy, medical applications, toxicology, and antipathogenic capabilities. The two main areas of pharmacology are pharmacodynamics and pharmacokinetics. Pharmacodynamics studies the effects of a drug on biological systems, and pharmacokinetics studies the effects of biological systems on a drug. In broad terms, pharmacodynamics discusses the chemicals with biological receptors, and pharmacokinetics discusses the liberation, absorption, distribution, metabolism, and excretion (LADME) of chemicals from the biological systems.
Pharmacology is not synonymous with pharmacy, though the two terms are frequently confused. Pharmacology is a branch of medical and biological sciences which encompasses the research, discovery, and characterization of chemicals exhibiting biological effects, alongside the elucidation of cellular and organismal function in relation to these chemicals. In contrast, pharmacy, a health services profession, is concerned with the application of the principles learned from pharmacology, pharmaceutics, medicinal chemistry, pharmacognosy, clinical pharmacy and others in its clinical settings; whether it be in a dispensing or clinical care role. In either field, the primary contrast between the two is their distinction between direct-patient care, pharmacy practice, and the science-oriented research field, driven by pharmacology.

== Etymology ==

The word pharmacology is derived from Greek word φάρμακον,  pharmakon, meaning "drug" or "poison", together with another Greek word -λογία, logia with the meaning of "study of" or "knowledge of" (cf. the etymology of pharmacy). Pharmakon is related to pharmakos, the ritualistic sacrifice or exile of a human scapegoat or victim in Ancient Greek religion.
The modern term pharmacon is used more broadly than the term drug because it includes endogenous substances, and biologically active substances which are not used as drugs.  Typically it includes pharmacological agonists and antagonists, but also enzyme inhibitors (such as monoamine oxidase inhibitors).

== History ==

The origins of clinical pharmacology date back to the Middle Ages, with pharmacognosy, Avicenna's The Canon of Medicine, Peter of Spain's Commentary on Isaac, and John of St Amand's Commentary on the Antedotary of Nicholas. Early pharmacology focused on herbalism and natural substances, mainly plant extracts while medicines were compiled in books called pharmacopoeias. Crude drugs have been used since prehistory as a preparation of substances from natural sources. However, the active pharmaceutical ingredient (API) of crude drugs are not purified and the substance is adulterated with other substances.
Traditional medicine varies between cultures and may be specific to a particular culture, such as in traditional Chinese, Mongolian, Tibetan, and Korean medicine. However much of this has since been regarded as pseudoscience. Pharmacological substances known as entheogens may have spiritual and religious use and a historical context.
In the 17th century, the English physician Nicholas Culpeper translated and used pharmacological texts. Culpeper detailed plants and the conditions they could treat. In the 18th century, much of clinical pharmacology was established by the work of William Withering. Pharmacology as a scientific discipline did not further advance until the mid-19th century amid the great biomedical resurgence of that period. Before the second half of the nineteenth century, the remarkable potency and specificity of the actions of drugs such as morphine, quinine, and digitalis were explained vaguely and with reference to extraordinary chemical powers and affinities to certain organs or tissues. The first pharmacology department was set up by Rudolf Buchheim in 1847, at the University of Tartu, in recognition of the need to understand how therapeutic drugs and poisons produced their effects. Subsequently, the first pharmacology department in England was set up in 1905 at University College London.
Pharmacology developed in the 19th century as a biomedical science that applied the principles of scientific experimentation to therapeutic contexts. The advancement of research techniques propelled pharmacological research and understanding. The development of the organ bath preparation, where tissue samples are connected to recording devices, such as a myograph, and physiological responses are recorded after drug application, allowed analysis of drugs' effects on tissues. The development of the ligand binding assay in 1945 allowed quantification of the binding affinity of drugs at chemical targets. Modern pharmacologists use techniques from genetics, molecular biology, biochemistry, and other advanced tools to transform information about molecular mechanisms and targets into therapies directed against disease, defects or pathogens, and create methods for preventive care, diagnostics, and ultimately personalized medicine.

== Divisions ==

The discipline of pharmacology can be divided into many sub disciplines each with a specific focus.

=== Systems of the body ===
Pharmacology can focus on specific systems comprising the body. Divisions related to bodily systems study the effects of drugs in different systems of the body. These include neuropharmacology, in the central and peripheral nervous systems; immunopharmacology in the immune system. Other divisions include cardiovascular, renal, and endocrine pharmacology. Psychopharmacology is the study of the use of drugs that affect the psyche, mind, and behavior (e.g. antidepressants) in treating mental disorders (e.g. depression). It incorporates approaches and techniques from neuropharmacology, animal behavior and behavioral neuroscience, and is interested in the behavioral and neurobiological mechanisms of action of psychoactive drugs. The related field of neuropsychopharmacology focuses on the effects of drugs at the overlap between the nervous system and the psyche.
Pharmacometabolomics, also known as pharmacometabolomics, is a field which stems from metabolomics, the quantification and analysis of metabolites produced by the body. It refers to the direct measurement of metabolites in an individual's bodily fluids, in order to predict or evaluate the metabolism of pharmaceutical compounds, and to better understand the pharmacokinetic profile of a drug. Pharmacometabolomics can be applied to measure metabolite levels following the administration of a drug, in order to monitor the effects of the drug on metabolic pathways. Pharmacomicrobiomics studies the effect of microbiome variations on drug disposition, action, and toxicity. Pharmacomicrobiomics is concerned with the interaction between drugs and the gut microbiome. Pharmacogenomics is the application of genomic technologies to drug discovery and further characterization of drugs related to an organism's entire genome. For pharmacology regarding individual genes, pharmacogenetics studies how genetic variation gives rise to differing responses to drugs. Pharmacoepigene


Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population, and application of this knowledge to prevent diseases.
It is a cornerstone of public health, and shapes policy decisions and evidence-based practice by identifying risk factors for disease and targets for preventive healthcare. Epidemiologists help with study design, collection, and statistical analysis of data, amend interpretation and dissemination of results (including peer review and occasional systematic review). Epidemiology has helped develop methodology used in clinical research, public health studies, and, to a lesser extent, basic research in the biological sciences.
Major areas of epidemiological study include disease causation, transmission, outbreak investigation, disease surveillance, environmental epidemiology, forensic epidemiology, occupational epidemiology, screening, biomonitoring, and comparisons of treatment effects such as in clinical trials. Epidemiologists rely on other scientific disciplines like biology to better understand disease processes, statistics to make efficient use of the data and draw appropriate conclusions, social sciences to better understand proximate and distal causes, and engineering for exposure assessment.
Epidemiology, literally meaning 'the study of what is upon the people', is derived from Greek  epi 'upon, among',   demos 'people' and  logos 'study', referring to the study of human populations. However, the term is widely used in studies of zoological populations (veterinary epidemiology), although the term 'epizootiology' was historically used. 'Epidemiology' has also been applied to studies of plant populations (botanical or plant disease epidemiology).
The distinction between "epidemic" and "endemic" was first drawn by Hippocrates, The term "epidemiology" appears to have first been used to describe the study of epidemics in 1802 by the Spanish physician Joaquín de Villalba in Epidemiología Española. Epidemiologists also study the interaction of diseases in a population, a condition known as a syndemic.
The term epidemiology is now widely applied to cover the description and causation of not only epidemic, infectious disease, but of disease in general, including related conditions and, especially since the 20th century, chronic diseases such as diabetes, cardiovascular disease, and cancer. Some examples of topics examined through epidemiology include high blood pressure, mental illness and obesity. Therefore, this epidemiology is based upon how the pattern of the disease causes change in the function of human beings.

== History ==
The Greek physician Hippocrates, taught by Democritus, was known as the father of medicine, sought a logic to sickness; he is the first person known to have examined the relationships between the occurrence of disease and environmental influences. Hippocrates believed sickness of the human body to be caused by an imbalance of the four humors (black bile, yellow bile, blood, and phlegm). The cure to the sickness was to remove or add the humor in question to balance the body. This belief led to the application of bloodletting and dieting in medicine. He coined the terms endemic (for diseases usually found in some places but not in others) and epidemic (for diseases that are seen at some times but not others).

=== Modern era ===

In the middle of the 16th century, a doctor from Verona named Girolamo Fracastoro was the first to propose a theory that the very small, unseeable, particles that cause disease were alive. They were considered to be able to spread by air, multiply by themselves and to be destroyable by fire. In this way he refuted Galen's miasma theory (poison gas in sick people). In 1543 he wrote a book De contagione et contagiosis morbis, in which he was the first to promote personal and environmental hygiene to prevent disease. The development of a sufficiently powerful microscope by Antonie van Leeuwenhoek in 1675 provided visual evidence of living particles consistent with a germ theory of disease.
During the Ming dynasty, Wu Youke (1582–1652) developed the idea that some diseases were caused by transmissible agents, which he called Li Qi (戾气 or pestilential factors) when he observed various epidemics rage around him between 1641 and 1644. His book Wen Yi Lun (瘟疫论, Treatise on Pestilence/Treatise of Epidemic Diseases) can be regarded as the main etiological work that brought forward the concept. His concepts were still being considered in analysing SARS outbreak by WHO in 2004 in the context of traditional Chinese medicine.
Another pioneer, Thomas Sydenham (1624–1689), was the first to distinguish the fevers of Londoners in the later 1600s. His theories on cures of fevers met with much resistance from traditional physicians at the time. He was not able to find the initial cause of the smallpox fever he researched and treated.
John Graunt, a haberdasher and amateur statistician, published Natural and Political Observations ... upon the Bills of Mortality in 1662. In it, he analysed the mortality rolls in London before the Great Plague, presented one of the first life tables, and reported time trends for many diseases, new and old. He provided statistical evidence for many theories on disease, and also refuted some widespread ideas on them.

John Snow is famous for his investigations into the causes of the 19th-century cholera epidemics, and is also known as the father of (modern) Epidemiology. He began with noticing the significantly higher death rates in two areas supplied by Southwark Company. His identification of the Broad Street pump as the cause of the Soho epidemic is considered the classic example of epidemiology. Snow used chlorine in an attempt to clean the water and removed the handle; this ended the outbreak. This has been perceived as a major event in the history of public health and regarded as the founding event of the science of epidemiology, having helped shape public health policies around the world. However, Snow's research and preventive measures to avoid further outbreaks were not fully accepted or put into practice until after his death due to the prevailing Miasma Theory of the time, a model of disease in which poor air quality was blamed for illness. This was used to rationalize high rates of infection in impoverished areas instead of addressing the underlying issues of poor nutrition and sanitation, and was proven false by his work.
Other pioneers include Danish physician Peter Anton Schleisner, who in 1849 related his work on the prevention of the epidemic of neonatal tetanus on the Vestmanna Islands in Iceland. Another important pioneer was Hungarian physician Ignaz Semmelweis, who in 1847 brought down infant mortality at a Vienna hospital by instituting a disinfection procedure. His findings were published in 1850, but his work was ill-received by his colleagues, who discontinued the procedure. Disinfection did not become widely practiced until British surgeon Joseph Lister, aided by his colleague, chemist Thomas Anderson, was able to "discover" antiseptics in 1865 based on the earlier work of Louis Pasteur.
In the early 20th century, mathematical methods were introduced into epidemiology by Ronald Ross, Janet Lane-Claypon, Anderson Gray McKendrick, and others. In 1927, William Ogilvy Kermack and Anderson Gray McKendrick published the foundational SIR (Susceptible-Infected-Recovered) model, applying mass-action kinetics from chemistry to disease transmission in populations. In a parallel development during the 1920s, German-Swiss pathologist Max Askanazy and others founded the International Society for Geographical Pathology to systematically investigate the geographical pathology of cancer and other non-infectious diseases across populations in different regions. After World War II, Richard Doll and other non-pathologists joined the field and advanced methods to stu


Technology is the application of conceptual knowledge to achieve practical goals, especially in a reproducible way. The word technology can also mean the products resulting from such efforts, including both tangible tools such as utensils or machines, and intangible ones such as software. Technology plays a critical role in science, engineering, and everyday life.
Technological advancements have led to significant changes in society. The earliest known technology is the stone tool, used during prehistory, followed by the control of fire—which in turn contributed to the growth of the human brain and the development of language during the Ice Age, according to the cooking hypothesis. The invention of the wheel in the Bronze Age allowed greater travel and the creation of more complex machines. More recent technological inventions, including the printing press, telephone, and the Internet, have lowered barriers to communication and ushered in the knowledge economy.
While technology contributes to economic development and improves human prosperity, it can also have negative impacts such as pollution and resource depletion, and can cause social harms like technological unemployment resulting from automation. As a result, philosophical and political debates about the role and use of technology, the ethics of technology, and ways to mitigate its downsides are ongoing.

== Etymology ==
Technology is a term dating back to the early 17th century that meant 'systematic treatment' (from Greek Τεχνολογία, from the Greek: τέχνη, romanized: tékhnē, lit. 'craft, art' and -λογία (-logíā), 'study, knowledge'). It is predated in use by the Ancient Greek word τέχνη (tékhnē), used to mean 'knowledge of how to make things', which encompassed activities like architecture.
Starting in the 19th century, continental Europeans started using the terms Technik (German) or technique (French) to refer to a 'way of doing', which included all technical arts, such as dancing, navigation, or printing, whether or not they required tools or instruments. At the time, Technologie (German and French) referred either to the academic discipline studying the "methods of arts and crafts", or to the political discipline "intended to legislate on the functions of the arts and crafts." The distinction between Technik and Technologie is absent in English, and so both were translated as technology. The term was previously uncommon in English and mostly referred to the academic discipline, as in the Massachusetts Institute of Technology.
In the 20th century, as a result of scientific progress and the Second Industrial Revolution, technology stopped being considered a distinct academic discipline and took on the meaning: the systemic use of knowledge to practical ends.

== History ==

=== Prehistoric ===

Tools were initially developed by hominids through observation and trial and error. Around 2 Mya (million years ago), they learned to make the first stone tools by hammering flakes off a pebble, forming a sharp hand axe. This practice was refined 75 kya (thousand years ago) into pressure flaking, enabling much finer work.
The discovery of fire was described by Charles Darwin as "possibly the greatest ever made by man". Archaeological, dietary, and social evidence point to "continuous [human] fire-use" at least 1.5 Mya. Fire, fueled with wood and charcoal, allowed early humans to cook their food to increase its digestibility, improving its nutrient value and broadening the number of foods that could be eaten. The cooking hypothesis proposes that the ability to cook promoted an increase in hominid brain size, though some researchers find the evidence inconclusive. Archaeological evidence of hearths was dated to 790 kya; researchers believe this is likely to have intensified human socialization and may have contributed to the emergence of language.
Other technological advances made during the Paleolithic era include clothing and shelter. No consensus exists on the approximate time of adoption of either technology, but archaeologists have found archaeological evidence of clothing 90-120 kya and shelter 450 kya. As the Paleolithic era progressed, dwellings became more sophisticated and more elaborate; as early as 380 kya, humans were constructing temporary wood huts. Clothing, adapted from the fur and hides of hunted animals, helped humanity expand into colder regions; humans began to migrate out of Africa around 200 kya, initially moving to Eurasia.

=== Neolithic ===

The Neolithic Revolution (or First Agricultural Revolution) brought about an acceleration of technological innovation, and a consequent increase in social complexity. The invention of the polished stone axe was a major advance that allowed large-scale forest clearance and farming. This use of polished stone axes increased greatly in the Neolithic but was originally used in the preceding Mesolithic in some areas such as Ireland. Agriculture fed larger populations, and the transition to sedentism allowed for the simultaneous raising of more children, as infants no longer needed to be carried around by nomads. Additionally, children could contribute labor to the raising of crops more readily than they could participate in hunter-gatherer activities.
With this increase in population and availability of labor came an increase in labor specialization. What triggered the progression from early Neolithic villages to the first cities, such as Uruk, and the first civilizations, such as Sumer, is not specifically known; however, the emergence of increasingly hierarchical social structures and specialized labor, of trade and war among adjacent cultures, and the need for collective action to overcome environmental challenges such as irrigation, are all thought to have played a role.
The invention of writing led to the spread of cultural knowledge and became the basis for history, libraries, schools, and scientific research.
Continuing improvements led to the furnace and bellows and provided, for the first time, the ability to smelt and forge gold, copper, silver, and lead – native metals found in relatively pure form in nature. The advantages of copper tools over stone, bone and wooden tools were quickly apparent to early humans, and native copper was probably used from near the beginning of Neolithic times (about 10 kya). Native copper does not naturally occur in large amounts, but copper ores are quite common and some of them produce metal easily when burned in wood or charcoal fires. Eventually, the working of metals led to the discovery of alloys such as bronze and brass (about 4,000 BCE). The first use of iron alloys such as steel dates to around 1,800 BCE.

=== Ancient ===

After harnessing fire, humans discovered other forms of energy. The earliest known use of wind power is the sailing ship; the earliest record of a ship under sail is that of a Nile boat dating to around 7,000 BCE. From prehistoric times, Egyptians likely used the power of the annual flooding of the Nile to irrigate their lands, gradually learning to regulate much of it through purposely built irrigation channels and "catch" basins. The ancient Sumerians in Mesopotamia used a complex system of canals and levees to divert water from the Tigris and Euphrates rivers for irrigation.
Archaeologists estimate that the wheel was invented independently and concurrently in Mesopotamia (in present-day Iraq), the Northern Caucasus (Maykop culture), and Central Europe. Time estimates range from 5,500 to 3,000 BCE with most experts putting it closer to 4,000 BCE. The oldest artifacts with drawings depicting wheeled carts date from about 3,500 BCE. More recently, the oldest-known wooden wheel in the world as of 2024 was found in the Ljubljana Marsh of Slovenia; Austrian experts have established that the wheel is between 5,100 and 5,350 years old.
The invention of the wheel revolutionized trade and war. It did not take long to discover that wheeled wagons could be used to carry heavy lo


Computer science is the study of computation, information, and automation. Included broadly in the sciences, computer science spans theoretical disciplines (such as algorithms, theory of computation, and information theory) to applied disciplines (including the design and implementation of hardware and software). An expert in the field is known as a computer scientist.
Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and preventing security vulnerabilities. Computer graphics and computational geometry address the generation of images. Programming language theory considers different ways to describe computational processes, and database theory concerns the management of repositories of data. Human–computer interaction investigates the interfaces through which humans and computers interact, and software engineering focuses on the design and principles behind developing software. Areas such as operating systems, networks and embedded systems investigate the principles and design behind complex systems. Computer architecture describes the construction of computer components and computer-operated equipment. Artificial intelligence and machine learning aim to synthesize goal-orientated processes such as problem-solving, decision-making, environmental adaptation, planning and learning found in humans and animals. Within artificial intelligence, computer vision aims to understand and process image and video data, while natural language processing aims to understand and process textual and linguistic data.
The fundamental concern of computer science is determining what can and cannot be automated. The Turing Award is generally recognized as the highest distinction in computer science.

== History ==

The earliest foundations of what would become computer science predate the invention of the modern digital computer. Machines for calculating fixed numerical tasks such as the abacus have existed since antiquity, aiding in computations such as multiplication and division. Algorithms for performing computations have existed since antiquity, even before the development of sophisticated computing equipment.
Wilhelm Schickard designed and constructed the first working mechanical calculator in 1623. In 1673, Gottfried Leibniz demonstrated a digital mechanical calculator, called the Stepped Reckoner. Leibniz may be considered the first computer scientist and information theorist, because of various reasons, including the fact that he documented the binary number system, although Thomas Harriot had already done so decades earlier. In 1820, Thomas de Colmar launched the mechanical calculator industry when he invented his simplified arithmometer, the first calculating machine strong enough and reliable enough to be used daily in an office environment. Charles Babbage started the design of the first automatic mechanical calculator, his Difference Engine, in 1822, which eventually gave him the idea of the first programmable mechanical calculator, his Analytical Engine. He started developing this machine in 1834, and "in less than two years, he had sketched out many of the salient features of the modern computer". "A crucial step was the adoption of a punched card system derived from the Jacquard loom", making it infinitely programmable. In 1843, during the translation of a French article on the Analytical Engine, Ada Lovelace wrote, in one of the many notes she included, an algorithm to compute the Bernoulli numbers, which is considered to be the first published algorithm ever specifically tailored for implementation on a computer. Around 1885, Herman Hollerith invented the tabulator, which used punched cards to process statistical information; eventually his company became part of IBM. Following Babbage, although unaware of his earlier work, Percy Ludgate in 1909 published the second of the only two designs for mechanical analytical engines in history. In 1914, the Spanish engineer Leonardo Torres Quevedo published his Essays on Automatics, and designed, inspired by Babbage, a theoretical electromechanical calculating machine which was to be controlled by a read-only program. The paper also introduced the idea of floating-point arithmetic. In 1920, to celebrate the 100th anniversary of the invention of the arithmometer, Torres presented in Paris the Electromechanical Arithmometer, a prototype that demonstrated the feasibility of an electromechanical analytical engine, on which commands could be typed and the results printed automatically. In 1937, one hundred years after Babbage's impossible dream, Howard Aiken convinced IBM, which was making all kinds of punched card equipment and was also in the calculator business to develop his giant programmable calculator, the ASCC/Harvard Mark I, based on Babbage's Analytical Engine, which itself used punched cards and a central processing unit. When the machine was finished, some hailed it as "Babbage's dream come true".
During the 1940s, with the development of new and more powerful computing machines such as the Atanasoff–Berry computer and ENIAC, the term computer came to refer to the machines rather than their human predecessors. As it became clear that computers could be used for more than just mathematical calculations, the field of computer science broadened to study computation in general. In 1945, IBM founded the Watson Scientific Computing Laboratory at Columbia University in New York City. The renovated fraternity house on Manhattan's West Side was IBM's first laboratory devoted to pure science. The lab is the forerunner of IBM's Research Division, which today operates research facilities around the world. Ultimately, the close relationship between IBM and Columbia University was instrumental in the emergence of a new scientific discipline, with Columbia offering one of the first academic-credit courses in computer science in 1946. Computer science began to be established as a distinct academic discipline in the 1950s and early 1960s. The world's first computer science degree program, the Cambridge Diploma in Computer Science, began at the University of Cambridge Computer Laboratory in 1953. The first computer science department in the United States was formed at Purdue University in 1962. Since practical computers became available, many applications of computing have become distinct areas of study in their own rights.

== Etymology and scope ==

Although first proposed in 1956, the term "computer science" appears in a 1959 article in Communications of the ACM, in which Louis Fein argues for the creation of a Graduate School in Computer Sciences analogous to the creation of Harvard Business School in 1921. Louis justifies the name by arguing that, like management science, the subject is applied and interdisciplinary in nature, while having the characteristics typical of an academic discipline. This effort, and those of others such as numerical analyst George Forsythe, were successful, and universities went on to create such departments, starting with Purdue in 1962. Despite its name, a significant amount of computer science does not involve the study of computers themselves. Because of this, several alternative names have been proposed. Certain departments of major universities prefer the term computing science, to emphasize precisely that difference. Danish scientist Peter Naur suggested the term datalogy, to reflect the fact that the scientific discipline revolves around data and data treatment, while not necessarily involving computers. The first scientific institution to use the term was the Department of Datalogy at the University of Copenhagen, founded in 1969, with Peter Naur being the first professor in datalogy. The term is used mainly in the Scandinavian countries. A


The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a network of networks that comprises private, public, academic, business, and government networks of local to global scope, linked by electronic, wireless, and optical networking technologies. The Internet carries a vast range of information services and resources, such as the interlinked hypertext documents and applications of the World Wide Web (WWW), electronic mail, discussion groups, internet telephony, streaming media and file sharing.
Most traditional communication media, including telephone, radio, television, paper mail, newspapers, and print publishing, have been transformed by the Internet, giving rise to new media such as email, online music, digital newspapers, news aggregators, and audio and video streaming websites. The Internet has enabled and accelerated new forms of personal interaction through instant messaging, Internet forums, and social networking services. Online shopping has also grown to occupy a significant market across industries, enabling firms to extend brick and mortar presences to serve larger markets. Business-to-business and financial services on the Internet affect supply chains across entire industries.
The origins of the Internet date back to research that enabled the time-sharing of computer resources, the development of packet switching, and the design of computer networks for data communication. The set of communication protocols to enable internetworking on the Internet arose from research and development commissioned in the 1970s by the Defense Advanced Research Projects Agency (DARPA) of the United States Department of Defense in collaboration with universities and researchers across the United States, United Kingdom and France.
The Internet has no single centralized governance in either technological implementation or policies for access and usage. Each constituent network sets its own policies. The overarching definitions of the two principal name spaces on the Internet, the Internet Protocol address (IP address) space and the Domain Name System (DNS), are directed by a maintainer organization, the Internet Corporation for Assigned Names and Numbers (ICANN). The technical underpinning and standardization of the core protocols is an activity of the non-profit Internet Engineering Task Force (IETF).

== Terminology ==

The word internetted was used as early as 1849, meaning interconnected or interwoven. The word Internet was used in 1945 by the United States War Department in a radio operator's manual, and in 1974 as the shorthand form of Internetwork. Today, the term Internet most commonly refers to the global system of interconnected computer networks, though it may also refer to any group of smaller networks.
The word Internet may be capitalized as a proper noun, although this is becoming less common. This reflects the tendency in English to capitalize new terms and move them to lowercase as they become familiar. The word is sometimes still capitalized to distinguish the global internet from smaller networks, though many publications, including the AP Stylebook since 2016, recommend the lowercase form in every case. In 2016, the Oxford English Dictionary found that, based on a study of around 2.5 billion printed and online sources, "Internet" was capitalized in 54% of cases.
The terms Internet and World Wide Web are often used interchangeably; it is common to speak of "going on the Internet" when using a web browser to view web pages. However, the World Wide Web, or the Web, is only one of a large number of Internet services. It is the global collection of web pages, documents and other web resources linked by hyperlinks and URLs.

== History ==

=== 1960s ===

In the 1960s, computer scientists began developing systems for time-sharing of computer resources. J. C. R. Licklider proposed the idea of a universal network while working at Bolt Beranek & Newman and, later, leading the Information Processing Techniques Office at the Advanced Research Projects Agency Network (ARPANET) of the United States Department of Defense. Research into packet switching, one of the fundamental Internet technologies, started in the work of Paul Baran at RAND in the early 1960s and, independently, Donald Davies at the United Kingdom's National Physical Laboratory in 1965.
After the Symposium on Operating Systems Principles in 1967, packet switching from the proposed NPL network was incorporated into the design of the ARPANET, an experimental resource sharing network proposed by ARPA. ARPANET development began with two network nodes which were interconnected between the University of California, Los Angeles and the Stanford Research Institute on 29 October 1969. The third site on the ARPANET was the Culler-Fried Interactive Mathematics Center at the University of California, Santa Barbara followed by the fourth, the Graphics Department at the University of Utah.

=== 1970s ===
By the end of 1971, 15 sites were connected to the young ARPANET, mainly in metropolitan areas of Los Angeles, San Francisco, and Boston. Thereafter, the ARPANET gradually developed into a decentralized communications network, connecting remote centers and military bases in the United States. Other user networks and research networks, such as the Merit Network and CYCLADES, were developed in the late 1960s and early 1970s. Early international collaborations for the ARPANET were rare. Connections were made in 1973 to Norway (NORSAR and, later, NDRE) and to Peter Kirstein's research group at University College London, which provided a gateway to British academic networks, the first internetwork for resource sharing.
ARPA projects, the International Network Working Group and commercial initiatives led to the development of various protocols and standards by which multiple separate networks could become a single network, or a network of networks. In 1974, Vint Cerf at Stanford University and Bob Kahn at DARPA published a proposal for "A Protocol for Packet Network Intercommunication". Cerf and his graduate students used the term internet as a shorthand for internetwork in RFC 675. The Internet Experiment Notes and later RFCs repeated this use. The work of Louis Pouzin and Robert Metcalfe had important influences on the resulting TCP/IP design. National PTTs and commercial providers developed the X.25 standard and deployed it on public data networks.

=== 1980s ===
The ARPANET initially served as a backbone for the interconnection of regional academic and military networks in the United States to enable resource sharing. Access to the ARPANET was expanded in 1981 when the National Science Foundation (NSF) funded the Computer Science Network (CSNET).
In 1982, the Internet Protocol Suite (TCP/IP) was standardized, which facilitated worldwide proliferation of interconnected networks. TCP/IP network access expanded again in 1986 when the National Science Foundation Network (NSFNet) provided access to supercomputer sites in the United States for researchers, first at speeds of 56 kbit/s and later at 1.5 Mbit/s and 45 Mbit/s.
The NSFNet expanded into academic and research organizations in Europe, Australia, New Zealand and Japan in 1988–89. Although other network protocols such as UUCP and PTT public data networks had global reach well before this time, this marked the beginning of the Internet as an intercontinental network. Commercial Internet service providers emerged in 1989 in the United States and Australia. The ARPANET was decommissioned in 1990.

=== 1990s ===

The linking of commercial networks and enterprises by the early 1990s, as well as the advent of the World Wide Web, marked the beginning of the transition to the modern Internet. Steady advances in semiconductor technology and optical networking created new economic opportunities for commercial involvement in


A blockchain is a distributed ledger with growing lists of records (blocks) that are securely linked together via cryptographic hashes. Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data (generally represented as a Merkle tree, where data nodes are represented by leaves). Since each block contains information about the previous block, they effectively form a chain (viz. linked list data structure), with each additional block linking to the ones before it. Consequently, blockchain transactions are resistant to alteration because, once recorded, the data in any given block cannot be changed retroactively without altering all subsequent blocks and obtaining network consensus to accept these changes.
Blockchains are typically managed by a peer-to-peer (P2P) computer network for use as a public distributed ledger, where nodes collectively adhere to a consensus algorithm protocol to add and validate new transaction blocks. Although blockchain records are not unalterable, since blockchain forks are possible, blockchains may be considered secure by design and exemplify a distributed computing system with high Byzantine fault tolerance.
A blockchain was created by a person (or group of people) using the name (or pseudonym) Satoshi Nakamoto in 2008 to serve as the public distributed ledger for bitcoin cryptocurrency transactions, based on previous work by Stuart Haber, W. Scott Stornetta, and Dave Bayer. The implementation of the blockchain within bitcoin made it the first digital currency to solve the double-spending problem without the need for a trusted authority or central server. The bitcoin design has inspired other applications and blockchains that are readable by the public and are widely used by cryptocurrencies. The blockchain may be considered a type of payment rail.
Private blockchains have been proposed for business use. Computerworld called the marketing of such privatized blockchains without a proper security model "snake oil"; however, others have argued that permissioned blockchains, if carefully designed, may be more decentralized and therefore more secure in practice than permissionless ones.

== History ==
Cryptographer David Chaum first proposed a blockchain-like protocol in his 1982 dissertation "Computer Systems Established, Maintained, and Trusted by Mutually Suspicious Groups". Further work on a cryptographically secured chain of blocks was described in 1991 by Stuart Haber and W. Scott Stornetta. They wanted to implement a system wherein document timestamps could not be tampered with. In 1992, Haber, Stornetta, and Dave Bayer incorporated Merkle trees into the design, which improved its efficiency by allowing several document certificates to be collected into one block. Under their company Surety, their document certificate hashes have been published in The New York Times every week since 1995.
The first decentralized blockchain was conceptualized by a person (or group of people) known as Satoshi Nakamoto in 2008. Nakamoto improved the design in an important way using a Hashcash-like method to timestamp blocks without requiring them to be signed by a trusted party and introducing a difficulty parameter to stabilize the rate at which blocks are added to the chain. The design was implemented the following year by Nakamoto as a core component of the cryptocurrency bitcoin, where it serves as the public ledger for all transactions on the network.
In August 2014, the bitcoin blockchain file size, containing records of all transactions that have occurred on the network, reached 20 GB (gigabytes). By 2024, the bitcoin blockchain exceeded 600 GB.
The words block and chain were used separately in Satoshi Nakamoto's original paper, but were eventually popularized as a single word, blockchain, by 2016.
According to Accenture, an application of the diffusion of innovations theory suggests that blockchains attained a 13.5% adoption rate within financial services in 2016, therefore reaching the early adopters' phase. Industry trade groups joined to create the Global Blockchain Forum in 2016, an initiative of the Chamber of Digital Commerce.
In May 2018, Gartner found that only 1% of CIOs indicated any kind of blockchain adoption within their organisations, and only 8% of CIOs were in the short-term "planning or [looking at] active experimentation with blockchain". For the year 2019 Gartner reported 5% of CIOs believed blockchain technology was a 'game-changer' for their business.

== Structure and design ==

A blockchain is a decentralized, distributed, and often public, digital ledger consisting of records called blocks that are used to record transactions across many computers so that any involved block cannot be altered retroactively, without the alteration of all subsequent blocks. This allows the participants to verify and audit transactions independently and relatively inexpensively. A blockchain database is managed autonomously using a peer-to-peer network and a distributed timestamping server. They are authenticated by mass collaboration powered by collective self-interests. Such a design facilitates robust workflow where participants' uncertainty regarding data security is marginal. The use of a blockchain removes the characteristic of infinite reproducibility from a digital asset. It confirms that each unit of value was transferred only once, solving the long-standing problem of double-spending. A blockchain has been described as a value-exchange protocol.
Logically, a blockchain can be seen as consisting of several layers:

infrastructure (hardware)
networking (node discovery, information propagation and verification)
consensus (proof of work, proof of stake)
data (blocks, transactions)
application (smart contracts/decentralized applications, if applicable)

=== Blocks ===
Blocks hold batches of valid transactions that are hashed and encoded into a Merkle tree. Each block includes the cryptographic hash of the prior block in the blockchain, linking the two. The linked blocks form a chain. This iterative process confirms the integrity of the previous block, all the way back to the initial block, which is known as the genesis block (Block 0). To assure the integrity of a block and the data contained in it, the block is usually digitally signed.
Sometimes separate blocks can be produced concurrently, creating a temporary fork. In addition to a secure hash-based history, any blockchain has a specified algorithm for scoring different versions of the history so that one with a higher score can be selected over others. Blocks not selected for inclusion in the chain are called orphan blocks. Peers supporting the database have different versions of the history from time to time. They keep only the highest-scoring version of the database known to them. Whenever a peer receives a higher-scoring version (usually the old version with a single new block added) they extend or overwrite their own database and retransmit the improvement to their peers. There is never an absolute guarantee that any particular entry will remain in the best version of history forever. Blockchains are typically built to add the score of new blocks onto old blocks and are given incentives to extend with new blocks rather than overwrite old blocks. Therefore, the probability of an entry becoming superseded decreases exponentially as more blocks are built on top of it, eventually becoming very low. For example, bitcoin uses a proof-of-work system, where the chain with the most cumulative proof-of-work is considered the valid one by the network. There are a number of methods that can be used to demonstrate a sufficient level of computation. Within a blockchain the computation is carried out redundantly rather than in the traditional segregated and parallel manner.

==== Block time ====
The block time is the average time it takes for the network to generate one extra block in the blockchain. By the time of block completion, the


Space exploration is the physical investigation of outer space by uncrewed robotic space probes and through human spaceflight.
While the observation of objects in space, known as astronomy, predates reliable recorded history, it was the development of large and relatively efficient rockets during the mid-twentieth century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, national prestige, uniting different nations, ensuring the future survival of humanity, and developing military and strategic advantages against other countries.
The early era of space exploration was driven by a "Space Race" in which the Soviet Union and the United States vied to demonstrate their technological superiority. Landmarks of this era include the launch of the first human-made object to orbit Earth, the Soviet Union's Sputnik 1, on 4 October 1957, and the first Moon landing by the American Apollo 11 mission on 20 July 1969. The Soviet space program achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Alexei Leonov) on 18 March 1965, the first automatic landing on another celestial body in 1966, and the launch of the first space station (Salyut 1) in 1971.
In the 1970s, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation, the foremost example being the International Space Station (ISS), built between 1998 and 2011.
The 2000s brought advancements in the national space-exploration programs of China, the European Union, Japan, and India. The 2010s saw the rise of the private space industry in earnest with the development of private launch vehicles, space capsules, and satellite manufacturing. In the 2020s, the two primary global programs gaining traction are Moon-focused: the Chinese-led International Lunar Research Station and the U.S.-led Artemis program, with its plan to build the Artemis Base Camp on the Moon, each with a set of international partners.

== History of exploration ==

=== First telescopes ===
The first telescope is said to have been invented in 1608 in the Netherlands by an eyeglass maker named Hans Lippershey, but their first recorded use in astronomy was by Galileo Galilei in 1609. In 1668 Isaac Newton built his own reflecting telescope, the first fully functional telescope of this kind, and a landmark for future developments due to its superior features over the previous Galilean telescope.
A string of discoveries in the Solar System (and beyond) followed, then and in the next centuries: the mountains of the Moon, the phases of Venus, the main satellites of Jupiter and Saturn, the rings of Saturn, many comets, the asteroids, the new planets Uranus and Neptune, and many more satellites.
The Orbiting Astronomical Observatory 2 was the first space telescope launched 1968, but the launch of the Hubble Space Telescope in 1990 set a milestone. As of 1 December 2022, there were 5,284 confirmed exoplanets discovered. The Milky Way is estimated to contain 100–400 billion stars and more than 100 billion planets. There are at least 2 trillion galaxies in the observable universe. HD1 is the most distant known object from Earth, reported as 33.4 billion light-years away.

=== First outer space flights ===

MW 18014 was a German V-2 rocket test launch that took place on 20 June 1944, at the Peenemünde Army Research Center in Peenemünde. It was the first human-made object to reach outer space, attaining an apogee of 176 kilometers, which is well above the Kármán line. It was a vertical test launch. Although the rocket reached space, it did not reach orbital velocity, and therefore returned to Earth in an impact, becoming the first sub-orbital spaceflight. In 1949, the Bumper-WAC reached an altitude of 393 kilometres (244 mi), becoming the first human-made object to enter space, according to NASA.

=== First object in orbit ===
The first successful orbital launch was of the Soviet uncrewed Sputnik 1 ("Satellite 1") mission on 4 October 1957. The satellite weighed about 83 kg (183 lb), and is believed to have orbited Earth at a height of about 250 km (160 mi). It had two radio transmitters (20 and 40 MHz), which emitted "beeps" that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data were encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on 3 January 1958.

=== First human outer space flight ===
The first successful human spaceflight was Vostok 1 ("East 1"), carrying the 27-year-old Russian cosmonaut, Yuri Gagarin, on 12 April 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin's flight resonated around the world; it was a demonstration of the advanced Soviet space program and it opened an entirely new era in space exploration: human spaceflight.

=== First astronomical body space explorations ===
The first artificial object to reach another celestial body was Luna 2 which reached the Moon in 1959. The first soft landing on another celestial body was performed by Luna 9 landing on the Moon on 3 February 1966. Luna 10 became the first artificial satellite of the Moon, entering in a lunar orbit on 3 April 1966.
The first crewed landing on another celestial body was performed by Apollo 11 on 20 July 1969, landing on the Moon. There have been a total of six spacecraft with humans landing on the Moon starting from 1969 to the last human landing in 1972.
The first interplanetary flyby was the 1961 Venera 1 flyby of Venus, though the 1962 Mariner 2 was the first flyby of Venus to return data (closest approach 34,773 kilometers). Pioneer 6 was the first satellite to orbit the Sun, launched on 16 December 1965. The other planets were first flown by in 1965 for Mars by Mariner 4, 1973 for Jupiter by Pioneer 10, 1974 for Mercury by Mariner 10, 1979 for Saturn by Pioneer 11, 1986 for Uranus by Voyager 2, 1989 for Neptune by Voyager 2. In 2015, the dwarf planets Ceres and Pluto were orbited by Dawn and passed by New Horizons, respectively. This accounts for flybys of each of the eight planets in the Solar System, the Sun, the Moon, and Ceres and Pluto (two of the five recognized dwarf planets).
The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7, which returned data to Earth for 23 minutes from Venus. In 1975, Venera 9 was the first to return images from the surface of another planet, returning images from Venus. In 1971, the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds. Later, much longer duration surface missions were achieved, including over six years of Mars surface operation by Viking 1 from 1975 to 1982 and over two hours of transmission from the surface of Venus by Venera 13 in 1982, the longest ever Soviet planetary surface mission. Venus and Mars are the two planets outside of Earth on which humans have conducted surface missions with uncrewed robotic spacecraft.

=== First space station ===
Salyut 1 was the first space station of any kind, launched into low Earth orbit by the Soviet Union on 19 April 1971. The International Space Station (ISS) is currently the largest and oldest of the 2 current fully functional space stations, inhabited continuously since the year 2000. The other, Tiangong space station built by China, is now fully crewed and operational.

=== First interstellar space flight ===
Voyager 1 became the first human-made object to leave the Solar System into interstellar space on 25 August 2012. The probe passed the heliop


In astronomy and cosmology, dark matter is an invisible and hypothetical form of matter that does not interact with electromagnetic radiation, including light. Dark matter is implied by gravitational effects that cannot be explained by general relativity unless more matter is present than can be observed. Such effects occur in the context of formation and evolution of galaxies, gravitational lensing, the observable universe's current structure, mass position in galactic collisions, the motion of galaxies within galaxy clusters, and cosmic microwave background anisotropies. Dark matter is thought to serve as gravitational scaffolding for cosmic structures. After the Big Bang, dark matter clumped into blobs along narrow filaments with superclusters of galaxies forming a cosmic web at scales on which entire galaxies appear like tiny particles.
In the standard Lambda-CDM model of cosmology, the mass–energy content of the universe is 5% ordinary matter, 26.8% dark matter, and 68.2% a form of energy known as dark energy. Thus, dark matter constitutes 85% of the total mass, while dark energy and dark matter constitute 95% of the total mass–energy content. While the density of dark matter is significant in the halo around a galaxy, its local density in the Solar System is much less than normal matter. The total of all the dark matter out to the orbit of Neptune would add up to about 1017 kg, the same as a large asteroid. Dark matter is classified as "cold", "warm", or "hot" according to velocity (more precisely, its free streaming length). Recent models have favored a cold dark matter scenario, in which structures emerge by the gradual accumulation of particles.
Dark matter is not known to interact with ordinary baryonic matter and radiation except through gravity, making it difficult to detect in the laboratory. The most prevalent explanation is that dark matter is some as-yet-undiscovered subatomic particle, such as either weakly interacting massive particles (WIMPs) or axions. The other main possibility is that dark matter is composed of primordial black holes.
Although the astrophysics community generally accepts the existence of dark matter, a minority of astrophysicists, intrigued by specific observations that are not well explained by ordinary dark matter, argue for various modifications of the standard laws of general relativity. These include modified Newtonian dynamics (MOND), tensor–vector–scalar gravity, and entropic gravity. So far, none of the proposed modified gravity theories can describe every piece of observational evidence at the same time, suggesting that even if gravity has to be modified, some form of dark matter would still be required.

== History ==

=== 1884 to 1940 ===
The hypothesis of dark matter has an elaborate history.
Lord Kelvin discussed the potential number of stars around the Sun in the appendices of a book based on a series of lectures given in 1884 in Baltimore. He inferred their density using the observed velocity dispersion of the stars near the Sun, assuming that the Sun was 20–100 million years old. He posed what would happen if there were a thousand million stars within 1 kiloparsec of the Sun (at which distance their parallax would be 1 milli-arcsecond). Kelvin concluded:

"Many of our supposed thousand million stars — perhaps a great majority of them — may be dark bodies."
In 1906, Henri Poincaré used the French term [matière obscure] ("dark matter") in discussing Kelvin's work. He concluded that the amount of dark matter would need to be less than that of visible matter, which was later found to be false.
The second to suggest the existence of dark matter using stellar velocities was Dutch astronomer Jacobus Kapteyn in 1922. A publication from 1930 by Swedish astronomer Knut Lundmark points to him being the first to hypothesize that the universe must contain much more mass than can be observed. Dutch radio astronomy pioneer Jan Oort also hypothesized the existence of dark matter in 1932. Oort was studying stellar motions in the galactic neighborhood and found the mass in the galactic plane must be greater than what was observed, but this measurement was later determined to be incorrect.

In 1933, Swiss astrophysicist Fritz Zwicky studied galaxy clusters while working at Caltech and made a similar inference. Zwicky applied the virial theorem to the Coma Cluster and obtained evidence of unseen mass he called dunkle Materie ('dark matter'). Zwicky estimated its mass based on the motions of galaxies near its edge and compared that to an estimate based on its brightness and number of galaxies. He estimated the cluster had about 400 times more mass than was visually observable. The gravity effect of the visible galaxies was far too small for such fast orbits, thus mass must be hidden from view. Based on these conclusions, Zwicky inferred some unseen matter provided the mass and associated gravitational attraction to hold the cluster together. Zwicky's estimates were off by more than an order of magnitude, mainly due to an obsolete value of the Hubble constant; the same calculation today shows a smaller fraction, using greater values for luminous mass. Nonetheless, Zwicky did correctly conclude from his calculation that most of the gravitational matter present was dark. However, unlike modern theories, Zwicky considered "dark matter" to be non-luminous ordinary matter.
Further indications of mass-to-light ratio anomalies came from measurements of galaxy rotation curves. In 1939, H.W. Babcock reported the rotation curve for the Andromeda Galaxy (then called the Andromeda Nebula), which suggested the mass-to-luminosity ratio increases radially. He attributed it to either light absorption within the galaxy or modified dynamics in the outer portions of the spiral, rather than to unseen matter. Following Babcock's 1939 report of unexpectedly rapid rotation in the outskirts of the Andromeda Galaxy and a mass-to-light ratio of 50; in 1940, Oort discovered and wrote about the large non-visible halo of NGC 3115.

=== 1970s ===
The hypothesis of dark matter largely took root in the 1970s. Several different observations were synthesized to argue that galaxies should be surrounded by halos of unseen matter. In two papers that appeared in 1974, this conclusion was drawn in tandem by independent groups: in Princeton, New Jersey, by Jeremiah Ostriker, Jim Peebles, and Amos Yahil, and in Tartu, Estonia, by Jaan Einasto, Enn Saar, and Ants Kaasik.

One of the observations that served as evidence for the existence of galactic halos of dark matter was the shape of galaxy rotation curves. These observations were done in optical and radio astronomy. In optical astronomy, Vera Rubin and Kent Ford worked with a new spectrograph to measure the velocity curve of edge-on spiral galaxies with greater accuracy.
At the same time, radio astronomers were making use of new radio telescopes to map the 21 cm line of atomic hydrogen in nearby galaxies. The radial distribution of interstellar atomic hydrogen (HI) often extends to much greater galactic distances than can be observed as collective starlight, expanding the sampled distances for rotation curves – and thus of the total mass distribution – to a new dynamical regime. Early mapping of the Andromeda Galaxy with the 300-foot (91 m) telescope at Green Bank and the 250-foot (76 m) dish at Jodrell Bank already showed the HI rotation curve did not trace the decline expected from Keplerian orbits.
As more sensitive receivers became available, Roberts & Whitehurst (1975) were able to trace the rotational velocity of Andromeda to 30 kpc, much beyond the optical measurements. Illustrating the advantage of tracing the gas disk at large radii; that paper's Figure 16 combines the optical data (the cluster of points at radii of less than 15 kpc with a single point further out) with the HI data between 20 and 30 kpc, exhibiting the flatness of the outer galaxy rotation curve; the solid curve peaking at t