(1):
(n.) The arrangement or relation of the parts of a machine; the parts of a machine, taken collectively; the arrangement or relation of the parts of anything as adapted to produce an effect; as, the mechanism of a watch; the mechanism of a sewing machine; the mechanism of a seed pod.
(2):
(n.) An ideal machine; a combination of movable bodies constituting a machine, but considered only with regard to relative movements.
(3):
(n.) Mechanical operation or action.