Cog (noun)

1. A tooth on the rim of a gear wheel or on the wheel of a ratchet, which meshes with other gears or teeth to transmit motion.
2. A tooth on the rim of a gear wheel or on the wheel of a ratchet, used to transmit motion from one wheel to another.
3. A toothed wheel that meshes with another toothed wheel to transmit motion.

Origin:

From middle english cogge, from old english *cogg, *cocc ("cog"), from proto-germanic *kukkaz ("cog"), from proto-indo-european *keg- ("to be crooked, bent").

Examples:

1. The cogs in the gear system were worn and needed to be replaced.
2. The cogs of a clockwork mechanism mesh with each other to keep time.
3. The cogs on the wheel were worn, causing the gears to slip.
4. The cogs are the key component of a gear system, they transfer power from the engine to the wheels.
5. The cogs on a bicycle's rear wheel transmit power from the pedals to the wheel, propelling the bike forward.