When all the points on a plane is at a fixed distance from the fixed point is called a circle.
The line that joins the centre of the circle and any point on the circle is called the radius.
A circle acts as a closure to all the points on the plane.
This closure can be classified into three categories:
1. The points that are interior to the circle.
2. The points that are on the circle.
3. The points that are outside the circle.
Some other components of the circle:
When a line segment connects any two points on the circle, then it is called a chord.
The diameter is the longest chord on the circle.
The line segment that passes through the centre of the circle connecting two definite points on the circle is called a diameter.