A tooth, cam, or catch for imparting or receiving motion, as on a gear wheel, or a lifter or wiper on a shaft; originally, a separate piece of wood set in a mortise in the face of a wheel.

For front cog see "Chain Ring". For rear cog see "Freewheel" or "Casette".

a sprocket located on the drive side of a rear hub.

tooth on the rim of gear wheel

a tooth on the rim of a wheel designed to mesh with another wheel to transmit or receive motion

tooth or radial support on wheel or gear.

a sprocket on the rear wheel's cassette or freewheel.

1. One of a series of teeth on the rim of a wheel, for transmitting or receiving motion by fitting between the teeth of another wheel. 2. A projection on a beam that fits into a corresponding groove or notch in another beam to make a joint.