dynamics - n.pl.
1 (usu. treated as sing.) a Mech. the branch of mechanics concerned with the motion of bodies under the action of forces (cf. STATICS). b the branch of any science in which forces or changes are considered (aerodynamics; population dynamics).
2 the motive forces, physical or moral, affecting behaviour and change in any sphere.
3 Mus. the varying degree of volume of sound in musical performance.

dynamicist n. (in sense 1).