Engine

An engine is a machine that produces mechanical force and motion from another form of energy (e.g. a fuel source, compressed air, or electricity).[1] It is also referred to as a prime mover. An automobile makes use of several motors to start the car and drive the car's various pumps – but the power plant that propels the car is called an engine. The term 'motor' was originally used to distinguish the new internal combustion engine-powered vehicles from earlier vehicles powered by a steam engine, such as the steam roller and motor roller. Historic military siege engines included large catapults, trebuchets, and battering rams.

The usage of the term "Engine"

Originally an engine was a mechanical device that converted force into motion. Military devices such as catapults are referred to as siege engines. The term "gin" as in cotton gin is recognised as a short form of the Old French word engin, in turn from the Latin ingenium, related to ingenious. Most devices used in the industrial revolution were referred to as an engine, and this is where the steam engine gained its name.

In more modern usage, the term is used to describe devices that perform mechanical work, follow-ons to the original steam engine. In most cases the work is supplied by exerting a torque, which is used to operate other machinery, generate electricity, pump water, or compress gas. In the context of propulsion systems, an air-breathing engine is one that uses atmospheric air to oxidise the fuel carried rather than supplying an independent oxidizer, as in a rocket.
The term is often used in computer science, designating such software as the "search engine", "3-D graphics game engine", "rendering engine" and "text-to-speech engine", even though these "engines" are not physically mechanical and cause only virtual action (this usage may have been derived from the "difference engine", an early mechanical computing device[citation needed]).