What is the difference between a motor and an engine? Does one create power and the other use it? Or are the words interchangeable?

This is a very difficult question. Some people would say that an engine must be a combustion engine, while a motor can be driven by electricity. If you have to distinguish between the two, that’s probably the best way to do it, though there are always going to be exceptions. Motor car, for example.

- PW

Michael Quinion, as one might expect, has written a wonderful and thorough article on this subject.

Here’s a snippet:

In everyday, non-technical usage the words have much the same meaning. But they have such clearly defined and fixed compounds (except in the rocket case) that they can’t be thought of as entirely interchangeable. The magazine article argues that the difference is that engines contain their own fuel or are part of a highly integrated engine-fuel system, whereas a motor draws on externally supplied energy. That’s the rule given in the Oxford English Dictionary, but on reflection it seems not wholly satisfactory. It doesn’t work for outboard motor or rocket motor for example. And it doesn’t explain why the two words should have been applied in this way. For that we have to look into their history.

And with that, I’ll leave you to do just that!

-Tim

In everyday language I would say Palewriter is correct: "engine" is generally only used for combustion engines, ie. ones which burn a fuel. The word combinations "petrol engine", "diesel engine" and "steam engine" trip very readily off the tongue. I think that in the past, it was used more in the sense that we would use "machine" today, for example a siege engine. I think talking about search engines would only complicate things!

"Motor" is something which produces movement. This could include engines, as in "motor car", but normally these days the assumption is that it is an electric motor, unless otherwise stated or implied. I have the feeling that "motor" was used much more often for what I would call an engine in the first half of last century, but since I wasn’t around at the time I can’t be sure without doing a lot of research.

Edited to add: Just look at that - no replies for eight hours, then two within a minute of each other. Still, I’m glad I haven’t entirely contradicted the famous Mr. Quinlon.

JtW.

Excellent work, Jonah.  You posted that message the same time I posted my reference to Michael Quinion’s article, and you hit on all the basic points in his article!

-Tim

;D