What is the difference between GENERATOR, MOTOR and ENGINE?

The industrial revolution saw a drastic increase in new inventions to do work using new methods involving electricity, steam and combustion. 1  This just confused all of us and now the terms are often used interchangeable in casual discourse and even in our own industry.  All three are machines that convert energy from one form to another but here are some simple delineations so that you can use the terms correctly. 
 
GENERATOR = Converts mechanical energy into electrical energy.  This is the opposite of a motor.  

• Examples: Power plants, backup generators, car alternator, regenerative braking, tachometers, crank flashlights, etc.
• The word generator comes from the Latin “generator” meaning begetter or producer. 2

MOTOR = Converts electrical energy into mechanical energy.  This is the opposite of a generator.  

• Examples: Electric car motor, ceiling fan, electric pumps, blender, drills, washing machine, AC compressor and blower fan, etc. 
• The word motor comes from the Latin “moto” meaning to set in motion. 3

ENGINE = Converts potential energy into mechanical energy.  This potential energy could be supplied by the combustion of fuel, another chemical reaction, or potential energy stored in water, air or steam. 

• Example: Reciprocating engines (Backup generators, cars), steam engines, gas turbines, airplanes, rockets, muscles, etc.

The word engine comes from the Latin “ingenium” meaning innate talent. 4
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