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SAI International Residential School
CLASS - IX
Mathematics
CHAPTER-6: Lines and Angles
Lesson Notes-1
Sub Topic: Basic Terms and definitions
1. Basic Terms and Definitions
(i) Line segment: A part of a line with two endpoints is called a line segment.
Line segment AB is denoted by .
(ii) Ray: A part of a line with one endpoint is called a ray.
The ray AB is denoted by .
(iii) Collinear points and non-collinear points: If three or more than three points
lie on the same line, then they are called collinear points, otherwise, they are non-
collinear points.
P, Q and R are collinear points.
A, B and C are non-collinear points.
