noun

geometrya threedimensional geometric shape that is perfectly symmetrical around its center.
A sphere is a threedimensional geometric shape that is perfectly symmetrical around its center. Every point on the surface of a sphere is the same distance from its center. This distance is known as the radius of the sphere. For example, in the case of a sphere with radius , any point on its surface is exactly units away from its center.
A circle is a basic shape used throughout mathematics. A circle is defined as a shape where every point along its perimeter is an equal distance from its center.