A sphere rotating around its axis

Rotation is the movement of an object in a circular motion.

A two-dimensional object rotates around a center (or point) of rotation. A three-dimensional object rotates around a line called an axis. If the axis of rotation is within the body, the body is said to rotate upon itself, or spin– which implies relative speed and perhaps free-movement with angular momentum. A circular motion about an external point (for example the Earth around the Sun) is called an orbit or more properly orbital revolution.