bevel gear, pinion and crown wheel, pinion and ring gear - gears that mesh at an angle

cog, sprocket - tooth on the rim of gear wheel

escape wheel - gear that engages a rocking lever

pinion - a gear with a small number of teeth designed to mesh with a larger wheel or rack

epicyclic gear, planet gear, planet wheel, planetary gear - an outer gear that revolves about a central sun gear of an epicyclic train

rack and pinion - a wheel gear (the pinion) meshes with a toothed rack; converts rotary to reciprocating motion (and vice versa)

spur gear, spur wheel - gear wheels that mesh in the same plane

sun gear - the central gear in a epicyclic train

tooth - one of a number of uniform projections on a gear

wheel - a simple machine consisting of a circular frame with spokes (or a solid disc) that can rotate on a shaft or axle (as in vehicles or other machines)

worm gear - gear consisting of a shaft with screw thread (the worm) that meshes with a toothed wheel (the worm wheel); changes the direction of the axis of rotary motion

worm wheel - gear with the thread of a worm