An engine is a mechanical device that produces some form of output from a given input. An engine whose purpose is to produce kinetic energy output from a fuel source is called a prime mover; alternatively, a motor is a device which produces kinetic energy from a preprocessed "fuel" (such as electricity, a flow of hydraulic fluid or compressed air).
An automobile has a starter motor, a windscreen wiper motor, and motors to drive pumps (fuel, power steering, windscreen washer)–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 (as in steam roller and motor roller).
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