---
source: ncert
topic: geometry
class_level: class_6
chapter: ch4
difficulty: beginner
---

Class 6 | Ch4: Basic Geometrical Ideas
Point: exact location, no size. Line: infinite both ways. Line segment: two endpoints. Ray: one endpoint infinite one way.
Angles: Acute(0-90), Right(90), Obtuse(90-180), Straight(180), Reflex(180-360), Complete(360).
Circle parts: Centre(fixed point), Radius(centre to circle), Diameter(chord through centre=2r), Chord(any two points on circle), Arc(part of circle), Sector(two radii + arc), Segment(chord + arc).
One line through two points. Infinite lines through one point.
Diameter is a chord but chord is not always diameter.