 Hello and welcome to the session. I'm Asha and I'm going to help you with the following question which says, give a definition. For each of the following terms, are there other terms that need to be defined first, what are they and how am I to define them? First is parallel lines, second perpendicular lines, third line segment, fourth radius of a circle and the fifth one is a square. Let us now begin with the solution and some other terms which need to be defined first before defining the given five terms are point, line, circle and correlator. So the definition of a point is a small dot made by a sharp pencil on a sheet of paper. A point has no dimension, it is only position. Second is a line and the basic concept about a line is that it should be straight and that it should extend indefinitely in both the directions. The third definition is of a circle and a circle is the set of all those points in a plane whose distance from a fixed point remains constant and the last one is a correlator and it is a closed figure made of four line segments. So these are some definitions with the help of which we will define the given five terms. First let us define parallel lines to be parallel, nonintersecting, they are coplanar. That is we have two lines L, M which are nonintersecting and a coplanar. Both lines L and M lies on the same plane and they do not intersect. So we can say that L is parallel to M. So this completes the first part and now let us define perpendicular lines. To be perpendicular they form a right angle at the point of intersection. Gloving figure shows intersecting at right angles. So we can say that L is perpendicular on M or M is perpendicular on L. So this completes the second part and now proceeding on to the third part where we have to define line segment. Line segment is a root of a line with two definite end points. Suppose we have a line L, two points A and B on L then this A B is called a line segment and this is called line segment A B or B A. So this completes the third part and now proceeding on to the fourth part where we have to define radius of a circle. The distance in the center between a circle is called the radius. That is if we have a circle over its center then at any point on the circle A and the line segment joining the center and this point A is called the radius of the circle. So this completes the fourth part. Now proceeding on to the last part where we have to define a square. A quadrilateral in which four angles, right angles, four sides are equal is called a square. So this is a quadrilateral having four sides. A, B, C, D is the quadrilateral in which angle D, angle C, angle B, angle A are all right angles and all the four line segments A, B, C, C, D and A, D are equal. So this is a square. So this completes the last part and hence the solution. Take care and have a good day.