Toothed wheel that transmits the turning movement of one shaft to another shaft. Gear wheels may be used in pairs, or in threes if both shafts are to turn in the same direction. The gear ratio —the ratio of the number of teeth on the two wheels— determines the torque ratio, the turning force on the output shaft compared with the turning force on the input shaft. The ratio of the angular velocities of the shafts is the inverse of the gear ratio.
The common type of gear for parallel shafts is the spur gear, with straight teeth parallel to the shaft axis. The helical gear has teeth cut along sections of a helix or corkscrew shape; the double form of the helix gear is the most efficient for energy transfer. Bevil gears, with tapering teeth set on the base of a cone, are used to connect intersecting shafts.
1. A mechanism for transmitting motion by gears for some specific purpose (as the steering gear of a vehicle); SYN. gear mechanism.
2. A toothed wheel that engages another toothed mechanism in order to change the speed or direction of transmitted motion; SYN. gear wheel, cogwheel.

ETYM Old Eng. gere, ger, AS. gearwe clothing, adornment, armor, from gearo, gearu, ready, yare; akin to Old High Germ. garawî, garwî ornament, dress. Related to Yare, Garb dress.
Miscellaneous articles needed for a particular operation or sport etc.; SYN. paraphernalia, appurtenances.

To set the level or character of; SYN. pitch.