A rotation is a 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 —which implies relative speed and perhaps free-movement with angular momentum. A circular motion about an external point, for example the Earth about the Sun, is called an orbit or more properly an orbital re… (More on Rotation)