 Hello and welcome to the session. In this session we will discuss circles. The collection of all the points in a plane which are fixed distance, fixed point is called a circle. This is a circle. The fixed point that will be point O is called the center of the circle and the fixed distance is called the radius of the circle. So in this case this O P is the radius of the circle. So we can define the radius of the circle as the line segment joining the center and any point on the circle is called radius of the circle. Basically a circle divides the plane on which it lies into three parts that is inside the circle that is this area which is called the interior of the circle then the circle and also outside the circle which is also called the exterior of the circle that is the portion outside the circle. If we take two points P and Q on the circle then the line segment joining the points P and Q is called the chord of the circle. So here we can say that P Q is the chord of the circle. Now let's define the diameter of the circle the chord which passes through the center of the circle the diameter of the circle. Like in this case P Q is the chord which is passing through the center O of the circle. So we say that P Q is the diameter of the circle. We have the diameter is the longest chord and all diameters have the same length diameter is equal to two times the radius of the circle. A piece of a circle between two points is called an arc. Consider the two points P and Q of the circle. Now we can say that there are two pieces one longer and the other smaller. This longer one that is this piece the major arc P Q and the shorter one that is this portion the minor arc P Q. Now major arc P Q is denoted by arc P R Q where arc is any point on the arc between P and Q and the minor arc P Q is denoted by this. When P and Q are the ends of a diameter then both arcs are equal and each is called a semi circle. That is this portion is a semi circle and also this portion is a semi circle. Then we have length of the complete circle circumference the region between a chord and segment of the circle and we have two types of segments major segment and minor segment. This portion that is this portion would be the minor segment and this portion is the major segment. Now the region between two radii joining the center end points is called a sector. Like segments we have minor arc corresponds to the minor sector that is this portion would be the minor sector the major arc corresponds to the major sector. So this portion would be the major sector. We have the two arcs are equal that is each is a semi circle when both the segments and both sectors become the same and each is known as a semi circular region. This completes the session hope you have understood what is a circle and different terms related to a circle.