dynamics

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. 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. n. The forces and motions that characterize a system: The dynamics of ocean waves are complex.
3. n. 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.
4. n. Variation in force or intensity, especially in musical sound.
5. n. Psychodynamics.

Century Dictionary and Cyclopedia

1. n. The mathematical theory of force; also (until recently the common acceptation), the theory of forces in motion; the science of deducing from given circumstances (masses, positions, velocities, forces, and constraints) the motions of a system of particles.
2. n. The moving moral or physical forces of any kind, or the laws which relate to them.

Wiktionary

1. n. mechanics The branch of mechanics that is concerned with the effects of forces on the motion of objects.
2. n. music The volume of the sound, such as piano, mezzo piano, mezzo forte, and forte.

GNU Webster's 1913

1. n. 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. n. The moving moral, as well as physical, forces of any kind, or the laws which relate to them.
3. n. (Mus.) That department of musical science which relates to, or treats of, the power of tones.

WordNet 3.0

1. n. the branch of mechanics concerned with the forces that cause motions of bodies