In classical mechanics, centrifugal force (from Latin centrum "center" an fugere "to flee") is an apparent force acting outward from the axis of a rotating reference frame. Centrifugal force is a fictitious force (also known as a pseudo force, inertial force or d'Alembert force) meaning that it is an artifact of acceleration of a reference frame. Unlike real forces such as gravitational or electromagnetic forces, fictitious forces do not originate from physical interactions between objects, and they do not appear in Newton's laws of motion for an inertial frame of reference; in an inertial frame, the motion of an object is explained by the real impressed forces. In a non-inertial frame, however, fictitious forces must be included along with the real forces in order to make accurate physical predictions. The fictitious forces present in a rotating reference frame with a uniform angular velocity are the centrifugal force and the Coriolis force, to which is added the Euler force when angular velocity is time dependent.