**Introduction to lines and angles**

Geometry is composed of two ancient Greek words: Geo and Metron. Geo means Earth and Metron means measurement. Geometry is the branch of mathematics which deals with shape, size, position, spatial relationships and properties of different figures.

The entire geometry begins with a point. A point is a dimensionless entity which specifies the location or position. It is represented using a dot symbol and its length is zero. All the shapes that we see around us consist of infinite number of points. When a point moves in such a manner that its direction remains unaltered then a straight line is obtained. In other words, a one-dimensional collection of points extending infinitely in both the directions represents a line as shown below. A line never ends.

Any two points on a line can uniquely specify it. In the fig. 1 given above, a line passing through these two points A and B is denoted as \(\overleftrightarrow{AB}\)

A portion of a line consisting of two end points is known as a line segment. Fig. 1 given above represents a line segment \(\overline{AB}\)

Ray is defined as a line segment with only one end point. Fig. 2 represents a ray with O as its end point and one side extending infinitely.

If a ray is rotated about its end point then the measure of its rotation between the final and initial position of the ray is known as an angle. In fig. 3, \(\overrightarrow{OB}\)

To solve more problems on topic Lines and Angles visit BYJU’S which provides detailed and step by step solutions to all questions in an NCERT Books. Also, take free tests to practice for exams.’