Circle
A circle is a round, two-dimensional geometric shape where all points on the boundary are at an equal distance, known as the radius, from a fixed central point.
Example
For a circle with a radius $r = 5\text{ cm}$, the circumference is $C = 2\pi r = 10\pi\text{ cm}$, and the area is $A = \pi r^2 = 25\pi\text{ cm}^2$.