eli5: What (if any) is the difference between an engine and a motor?


I’ve heard these words used interchangeably over the years, with engine being more prevalent. Is there any difference? Why is a small gas-driven device like a lawnmower commonly said to have a motor, while what is under the hood of a car is almost always referred to as an engine?

In: 160

IN GENERAL, motors run on electricity, and engines run on a fuel like gasoline or diesel.

So like electric toys or power tools have motors in them, which use electricity to make a magnet attached to a drive shaft spin.

While engines are what are in cars and lawn mowers and planes.

Now there’s some confusion in that “motorcycles” and “motorboats” have the word motor in them when they really have engines. But that’s just the name people gave them.


An engine is a machine that converts thermal energy into mechanical energy to produce forward motion. So an old steam train would have their entire unit that provided power called an engine. A motor is a rotating machine that transforms electricity energy into mechanical energy. Over the years the definitions have become somewhat ambiguous and the two terms tend to be interchanged but they do mean two very different things.

Engines contain their own power source while motors use an external power source. This is why a lot of people simplify it down to say “An engine is powered by gas but a motor is powered by electricity.”

If you convert a source of energy to some sort of motion, you’re a motor. If you can also convert that motion into an action, such as powering a mill or better yet mounting yourself on a rolling frame and trundling down the road, you’re an engine.

Edit: I found definitions that both agree with this, or say a motor is electric and an engine is combustion. Whatever.