Source : Webster's Revised Unabridged Dictionary (1913)

Dynamics \Dy*nam"ics\, n.
   1. That branch of mechanics which treats of the motion of
      bodies (kinematics) and the action of forces in producing
      or changing their motion (kinetics). Dynamics is held by
      some recent writers to include statics and not kinematics.

   2. The moving moral, as well as physical, forces of any kind,
      or the laws which relate to them.

   3. (Mus.) That department of musical science which relates
      to, or treats of, the power of tones.

Source : WordNet®

dynamics
     n : the branch of mechanics concerned with the forces that cause
         motions of bodies [syn: {kinetics}]