2.Give a definition for each of the following terms. Are there other terms that need to be defined first? What are they and how might you define them?
(i) Parallel lines
(ii) Perpendicular tines
(iii) Line segment
(v) Square

i)Parallel lines: Two lines in a plane are said to be parallel, if they have no point in common.
In figure, x and y are said to be parallel because they have no point in common and we write, x||y . Here, the term point is undefined.

ii)Perpendicular lines: Two lines in a plane are said to be perpendicular, if they intersect each other at a right angle.
In figure, P and Q are said to be perpendicular lines because they intersect each other at $$90^\circ$$.

iii)Line segment: The definite length between two points is called the line segment. ln figure, the definite length between A and B is line segment and represented by AB.

iv)Radius of a circle: The distance from the centre to a point on the circle is called the radius of the circle. ln the adjoining figure OA is the radius.

v)Square: A square can be defined as a rectangle having same length and breadth.