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An engine or motor, is a machine designed to convert one form of energy into mechanical energy.〔(Dictionary.com: (World heritage) ) "3. any device that converts another form of energy into mechanical energy so as to produce motion"〕 Heat engines, including internal combustion engines and external combustion engines (such as steam engines) burn a fuel to create heat, which then creates a force. Electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air and others—such as clockwork motors in wind-up toys—use elastic energy. In biological systems, molecular motors, like myosins in muscles, use chemical energy to create forces and eventually motion. ==Terminology== The word "engine" derives from Old French ''engin'', from the Latin ''ingenium''–the root of the word ''ingenious''. Pre-industrial weapons of war, such as catapults, trebuchets and battering rams, were called "siege engines", and knowledge of how to construct them were often treated as military secrets. The word "gin", as in "cotton gin", is short for "engine". Most mechanical devices invented during the industrial revolution were described as engines—the steam engine being a notable example. In modern usage, the term ''engine'' typically describes devices, like steam engines and internal combustion engines, that burn or otherwise consume fuel to perform mechanical work by exerting a torque or linear force (usually in the form of thrust). Examples of engines which exert a torque include the familiar automobile gasoline and diesel engines, as well as turboshafts. Examples of engines which produce thrust include turbofans and rockets. When the internal combustion engine was invented, the term "motor" was initially used to distinguish it from the steam engine—which was in wide use at the time, powering locomotives and other vehicles such as steam rollers. "Motor" and "engine" later came to be used interchangeably in casual discourse. However, technically, the two words have different meanings. An ''engine'' is a device that burns or otherwise consumes fuel, changing its chemical composition, whereas a motor is a device driven by electricity, air, or hydraulic pressure, which does not change the chemical composition of its energy source.〔"Engine", ''McGraw-Hill Concise Encyclopedia of Science and Technology'', Third Edition, Sybil P. Parker, ed. McGraw-Hill, Inc., 1994, p. 714.〕 However, rocketry uses the term rocket motor, even though they consume fuel. A heat engine may also serve as a ''prime mover''—a component that transforms the flow or changes in pressure of a fluid into mechanical energy.〔"Prime mover", ''McGraw-Hill Concise Encyclopedia of Science and Technology'', Third Edition, Sybil P. Parker, ed. McGraw-Hill, Inc., 1994, p. 1498.〕 An automobile powered by an internal combustion engine may make use of various motors and pumps, but ultimately all such devices derive their power from the engine. Another way of looking at it is that a motor receives power from an external source, and then converts it into mechanical energy, while an engine creates power from pressure (derived directly from the explosive force of combustion or other chemical reaction, or secondarily from the action of some such force on other substances such as air, water, or steam). Devices converting heat energy into motion are commonly referred to simply as ''engines''.〔Collins English Dictionary -Retrieved September 03, 2012 from CollinsDictionary.com website:http://www.collinsdictionary.com/dictionary/english/Engine 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Engine」の詳細全文を読む スポンサード リンク
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