A sphere is a perfectly
round shape. Objects which are in the shape of a sphere are called
spherical.

Balls, balloons and soap bubbles are often spherical. A
sphere is defined as the set of point P in space which are all the
same distance r from a fixed point O. O is the center of the sphere
r is its radius.

The area of the surface of the sphere is 4 π r^{2}

The volume enclosed by the sphere is 4/3 π r^{3}