1. 1. (used with a sing. verb) The branch of mechanics that is concerned with the effects of forces on the motion of a body or system of bodies, especially of forces that do not originate within the system itself. Also called kinetics.
   2. (used with a pl. verb) The forces and motions that characterize a system: The dynamics of ocean waves are complex.
2. (used with a pl. verb) The social, intellectual, or moral forces that produce activity and change in a given sphere: The dynamics of international trade have influenced our business decisions on this matter.
3. (used with a pl. verb) Variation in force or intensity, especially in musical sound.
4. (used with a sing. verb) Psychodynamics.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.