Kinematics: This is that branch of Theory of Machines that deals with the relative motion among the several machine parts; without referring forces or torques that cause motion.

Dynamics: This is that branch of Theory of Machines that deals along the forces and their effects, whereas acting on the machine parts in motion.

Kinematic Link: Each portion of a mechanism that moves relative to some other part is called a kinematic link or an element or simply link. A link can have several parts integral with each other that have no motion relative to one another.