Definitions via Wikipedia. See below in
Red. Seems both ways can be correct. In some engineering environments motor and engine are separate definitions, but in common use they are interchangeable.
Terminology[edit]
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 was often treated as a military secret. 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. However, the original steam engines, such as those by
Thomas Savery, were not mechanical engines but pumps. In this manner, a
fire engine in its original form was merely a water pump, with the engine being transported to the fire by horses.
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). Devices converting heat energy into motion are commonly referred to simply as
engines.
[3] 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. The term
motor derives from the Latin verb
moto which means to set in motion, or maintain motion. Thus a motor is a device that imparts motion.
Motor and engine are interchangeable in standard English.[4] In some engineering jargons, the two words have different meanings, in which engine is a device that burns or otherwise consumes fuel, changing its chemical composition, and a motor is a device driven by electricity, air, or hydraulic pressure, which does not change the chemical composition of its energy source.[5][6] 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.
[7] 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).
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