the result of mathematical differentiation; the instantaneous change of one quantity relative to another; df(x)/dx
a bevel gear that permits rotation of two shafts at different speeds; used on the rear axle of automobiles to allow wheels to rotate at different speeds on curves
a toothed wheel that engages another toothed mechanism in order to change the speed or direction of transmitted motion
equipment consisting of miscellaneous articles needed for a particular operation or sport etc.
a mechanism for transmitting motion for some specific purpose (as the steering gear of a vehicle)