My uncle worked at Estes, the hobby rocket company, for many years. He was always a stickler about calling the black powder propellant sources "motors" and indeed older motors are labeled such. [1] He insisted they were not engines as they had no moving parts and would always correct me when I said "rocket engine." He eventually explained that rocket engines exist, but they are engines with valves and pumps and use liquid fuel (e.g. the Saturn V's F-1 engines), while solid rockets (e.g. Estes' products, or the shuttle's SRBs) are simply motors since they merely consist of burning propellant and a nozzle. Indeed the wiki pages for the F-1 and the SRB are consistent in calling the former engine and the latter motor.

However, at some point since he retired, Estes transitioned to calling them Engine/Motors [2], and now, the primary labelling Estes uses calls them Engines, though Engine/Motor is still printed on the cardboard casing itself. [3]

Interestingly, the Spanish, French and German on the motors still use motor, as Motor, Moteur-Fusee and Raketenmotor, respectively.

Because of that upbringing, I have since treated the words to mean that a motor is something that provides force of motion (thrust or rotation) - it may or may not also be an engine, as in the rocketry examples. An engine is a contraption with moving/interacting parts that uses energy to accomplish some goal - that goal may (F-1, car engine) or may not (cotton gin, search engine) be the propulsion of the contraption itself and what it's attached to.

That said, as a child I made no such distinction, hence the frequent corrections. I am happy to recognize that in common vernacular they are usually synonymous, though it would still sound strange, I think, to call something a 'search motor' (edit: however, see comment by yau8edq12i !) or a 'graphics motor' just as it would be jarring to encounter 'servoengine'.




This was fascinating to me.

Also, I was apparently using my own personal definition of "engine" that was somewhat different than the other modern usage.

To me, a "motor" is something that translates energy into motion. An "engine" is something that translates energy into work. So a motor is a kind of engine, and uses of "engine" in knowledge work is an analogy.

Aren't there large areas of the anglophone world where "motor" = electric motor and "engine" = something that burns fuel to turn?
Was the article written by an llm difference engine? In that it failed at discussing the differences of the two and really just regurgitated the etymologies and ancient definitions of the two terms with no insight about modern usages. My quick difference as a matter of opinion only is that engine is related to carnot some heat cycle creates enables work that can be turned into locomotion. Motor is a superset, and is some system, process or machine that turns potential energy into kinetic energy. That is my opinion, of which i am open to, in fact very interested in reading others. Unfortunately this was not that article, instead you get a brief history lessons on words, with the thesis that some word's meanings change over time (allow me to pick my jaw off the floor) and don't worry about delineating the two terms because they pretty much mean the same thing. Not what i was expecting from mit engineering.
One thing that jumped out at me is that the word engine, in its historic understanding, would apply quite well to the Rube Goldberg drawings of overly complex contraptions to do various tasks... which means it would also apply to most enterprise architectures which are similarly overly complex.
In modern day usage, I would never refer to an electric motor as an electric engine or just engine, but I don't know why. Maybe just because I have never heard nor seen it used referred to as electric engine. So it just sounds/feels weird to say/type it. That is the opposite from definitely referring to an ICE as a motor.

English is just weird.

Fun fact: the French word engin still retains its original meaning of contrivance, contraption. But we still translate "search engine," which refers to this archaic English meaning, as moteur de recherche ("search motor").
Pretending that they are anything but synonyms now is ridiculous and I'm glad the article pointed out that they are used that way instead of pretending that the older definitions still have merit like so many prescriptionist folks do.
My native language is German. We only have the word Motor. Thought engine is just the 1:1 translation of it, but apparently not.
The way I see it:

A motor produces locomotion. It makes other things move.

An engine produces power. Locomotion can be derived from power but isn't required to.

A train locomotive might be referred to as a "locomotive engine".

A car with an internal combustion engine moves from power generated by that engine. But a car with electric motors does not have an engine because power is not produced there. Power is produced elsewhere and then stored in the battery. Locomotion is produced by consuming the stored power.

Of course, that's just my interpretation of the two words without referring to a dictionary.

> The OED lists a second definition of “engineer” as well. “It is synonymous with the older usage meaning ‘artifice,’” says Fuller. “An engineer is an author or designer of something, a person who contrives a plot, a schemer.” A definition one can only hope will soon pass from common usage.

I am not at all sure why.

This is an enormously valuable concept: that plots require both participants and also people who do not just direct it or order it, or even just design it, hands off (often called "the architect of the plot"). They need people who are there from start to finish, like an author is; involved in every corner.

In my usage, Engine is generally something that consumes gasoline (sometimes Diesel) and generate rotational power and lots of exhaust gas and heat.

I almost always use the term motor for an electromechanical machine that turns electrical into mechanical power.

Like all words, there's ambiguity to it.

In my language, everything is a motor and the "engine" root is only used in engineer.
A related bit of terminology I recently picked up[0] is "electric motor" vs. "electric machine", with the latter being preferred when the machine can function as either a motor or a generator (as is the case e.g. for most brushless DC motors).

[0]: I've been working my way through this book:

My understanding engine is a device governed by laws of thermodynamics, whereas motor is based on electrodynamics.

Always thought calling car engine a motor is incorrect, shouldn’t be used interchangeably. In my experience machinery would be common name for both in engineering terms, not daily usage.

Is a bicycle an engine (or a motor)? It is a machine with moving parts that converts power into motion.
Engine converts lower form of energy, like heat, into higher form of energy, like kinetic, at a loss. It’s shifting up

Motor converts equivalent forms of energy, or down, at very high efficiency. Electric to kinetic

> “Engine” is from the Latin ingenium: character, mental powers, talent, intellect, or cleverness.

And thus we get a common root for the words engine and genius. Fascinating.

If asked to craft a definition, I would offer that motors are electrical and use magnetism to induce rotation on an armature.

Engines are chemically driven and use some flavor of combination to rotate a shaft.

>> Today, the words are virtually synonymous.

Ehhh that's a stretch, unless we're talking Real Housewives type of "lay people".

As I understand it (within an engineering context), a "motor" converts electrical energy to mechanical energy, and an "engine" takes thermal/chemical/some other form of mechanical energy and outputs mechanical energy. But it's confusing because I've changed the "motor" in my old Honda when I was a teenager. So while I agree there is some nuance and blurry lines, not sure the two words are quite "interchangeable".