 Hi and welcome to the session. Today we will learn about circle. A circle is the path of a point moving at the same distance from a fixed point. Here this is the circle with a fixed point O. The fixed point is the center of the circle. So here O is the center of the circle, radius of the circle. So here O p is the radius of the circle. Here we have three more points on the circle q, r and s. Center to these points then O q is equal to O r is equal to O s is equal to O p as these all are the radius of the given circle. That is the fixed distance from the fixed point to the point on a circle. So that means we can say that radius is a line segment that connects the center to a point p is a line segment joining these two points and passing through the center of the circle that is O. So here is the diameter of the circle. Also diameter is twice of radius of the circle. Now let's see. So here suppose we have two points a and b then the line segment joining these two points that is the line segment a, b is the chord of the circle. Next we have n arc is a portion suppose we have two points a and b on the circle arc of the circle in the interior. Now here we have an arc a, b, a and b to the center of the circle portion will be the sector on one side and a pair of radii on the other two sides. Now radii radius interior pq now the region arc and the chord of the given circle and then again we have the point a word is the circumference of the given circle. Now here a, b is the diameter of the circle that is the diameter of the circle in two.