Dynamics [dahy-nam-iks] :
(used with a singular verb) Physics. the branch of mechanics that deals with the motion and equilibrium of systems under the action of forces, usually from outside the system.
(used with a plural verb) the motivating or driving forces, physical or moral, in any field.
(used with a plural verb) the pattern or history of growth, change, and development in any field.
(used with a plural verb) variation and gradation in the volume of musical sound.