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."