Rotation

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 around an external point (for example the Earth around the Sun) is called an orbit or more properly orbital revolution. As an extension, 4d rotations are around planes. Every rotation can also be described as in a plane and around a point.