Gear is a mechanical device that transmits power and motion between axes.

It is a toothed machine part that meshes with another toothed part to transmit motion or to change speed or direction. Materials for gears may include aluminum, brass, bronze, cast iron, carbon or alloy steel, hardened steel, stainless steel, and a wide variety of plastic materials.

Gear is a comprehensive term in general use on shipboard signifying the total of all implements, apparatus, mechanism, machinery, etc., appertaining to and employed in the performance of any given operation. For instance the brooms, brushes, buckets, dust pans, mops, etc., constitute the cleaning gear, the rudder, steering engine or motors, shafting, gears, drums, etc., the steering gear, etc.