Sphere

An image of a sphere

A sphere is a shape in space that is like the surface of a ball. Usually the terms ball and sphere are used alike. But in mathematics, the precise (exact) definition only allows points in the 3 dimensional space which are uniformly and symmetrically located at a fixed length called radius of the sphere.

Examples of these are basketballs, superballs, and playground balls.

In other places sphere means the earth.^[source?]

A sphere is the 3 dimensional analogue of a circle.

Volume

The volume of a sphere is given by the following formula

$\!V = \frac{4}{3}\pi r^3$

$\pi$ is a constant that is approximately equal to 3.1416.

Surface Area

Surface area of a sphere

The surface area of a sphere is given by the following formula

$\!A =4 \pi r^2$