kinetics (n.)

"relating to muscular motion," 1841, from Greek kinētikos "moving, putting in motion," from kinētos "moved," verbal adjective of kinein "to move" (from PIE root *keie- "to set in motion").

Buster Keaton's subject was kinetic man, a being he approached with the almost metaphysical awe we reserve for a Doppelgänger. This being was, eerily, himself, played by himself, then later in a projection room, watched by himself: an experience never possible to any generation of actors in the previous history of the world. [Hugh Kenner, "The Counterfeiters," 1968]

From 1855 as "causing motion." Related: Kinetical; kinetically.

in the names of sciences or disciplines (acoustics, aerobics, economics, etc.), a 16c. revival of the classical custom of using the neuter plural of adjectives with Greek -ikos "pertaining to" (see -ic) to mean "matters relevant to" and also as the titles of treatises about them. Subject matters that acquired their English names before c. 1500, however, tend to be singular in form (arithmetic, logic, magic, music, rhetoric). The grammatical number of words in -ics (mathematics is/mathematics are) is a confused question.