Cog-wheel, also known as a gear, is a mechanical component that transfers power and motion between different parts of a machine. There are various synonyms for the word cog-wheel such as gearwheel, toothed wheel, sprocket, pinion, and gear. Gearwheels are used in almost all mechanical devices, from cars to watches, to clocks and even factory machinery. A toothed wheel refers to a gear or cog that has teeth along its circumference used to transfer power from one component to another. A sprocket is a type of cog-wheel with teeth that mesh with a chain. Pinions are small gears that mesh with larger gears and transfer motion and power in a machine. The word gear can refer to any one of these variations of cog-wheels.