A Sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in three dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point.

This distance r is known as the radius of the sphere. The maximum straight distance through the sphere is known as the diameter of the sphere. It passes through the center and is thus twice the radius.

Higher mathematics makes a distinction between the sphere and the ball. Accordingly the former is a two-dimensional spherical surface embedded in three-dimensional Euclidean space and the latter is the three-dimensional shape consisting of a sphere and its interior.

In 3 dimensions, the volume inside a sphere, that is, the volume of the ball is given by the formula

r is the radius of the sphere and π is the constant pi. This formula was first derived by Archimedes, who showed that the volume of a sphere is 2/3 that of a circumscribed cylinder.

A sphere is a solid with all its points the same distance from the center.