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?
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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.
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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.
For the most part, they are interchangeable. However there is a distinction that may often affect which one is most appropriate to use.
A motor is something that moves, usually spins, and powers the movement of other components. A lawnmower has a motor because it moves the blades. An electric garage door has a motor because it moves the door up and down. A fan has a motor because it spins the fan.
Engines also move, usually spin, and move other components, but they do that specifically to *move* the thing they’re into, as in move it through space. Their purpose is locomotion. A car’s engine is an engine because it moves the car. A train engine is an engine because it moves the train. The engine’s primary function is locomotion.
However the distinction is also made between electric motors and gas powered (or steam) engines. Reciprocating engines are generally called engines (but can also be called motors) while electric motors are generally always called motors (and rarely ever engines).
So a diesel engine in a car? An engine. The same engine in a power generator? It’s a motor.
An electric motor in a lawnmower? A motor. A gas powered engine in a lawnmower? Still a motor, unless it’s a driving lawnmower in which case it’s an engine. An electric motor in a power drill? That’s a motor. An electric motor in an electric car? Well that’s still a motor because it feels weird to call it an engine.
**All engines are motors but not all motors are engines.**
Historically, motor and engine had different meanings. “Motor” was strictly related to movement and the word derives from the Latin: “movere” which is to move. We can see this usage in the modern term “motor neuron” which are neurons related to, you guessed it, movement.
Engine comes from the Latin: “ingenium” which means ability, talent, or character. While those meanings don’t quite make sense initially, they sort of do when you think about how we call medieval warfare devices “siege engines” or the modern term like “game engine.” A siege engine is a device that grants you the ability to siege, a game engine grants you the ability to write games. Historically, things like traps and lures were called engines. Thus, engine was the name for a device that imparts some kind of ability.
Now, coming back to internal combustion “engines” and/or “motors” we can see how something that converts an energy source into motion could both be a motor *or* an engine. It’s a motor because it creates motion. It’s an engine because it’s a device that imparts the ability to move. So, if using the historic origins of the words, an internal combustion device that creates motion is *both* an engine and a motor.
However, if you were to use engine or motor outside of the mechanical engineering realm (say, neurology or game development), motor is about motion and engine is about a device that imparts you with some ability.
EDIT: Sorry if this was ELI10. I forgot which sub I was in. Leaving it though because it answers the question.
EDIT2: I totally forgot more uses of engine that are *not* specifically motor related per se: “search engine”, “engineer”, Babbage’s “Analytical Engine” and “Difference Engine”.
It seems there are multiple definitions for both. My understanding has always been that all engines are motors but not all motors are engines. According to google they basically have the same definition (converting energy to motion) but I’ve never heard someone call an electric motor an engine.
In the context I hear a lot (propulsion) motors are simple and engines are complex. Motors directly convert fuel to motion while engines mix fuel/oxidizer ratios for controllability. A firework with solid fuel uses a rocket motor; a spaceship that mixed liquid fuel and oxidizer to throttle thrust uses a rocket engine.
From a purely physics standpoint, an engine is a mechanism that converts one form of energy to mechanical energy.
So, a Stirling engine takes a difference in temperature to produce motion. An internal combustion engine converts chemical potential energy into motion.
The term “motor” is often used to describe devices that convert electricity to motion.
In essence, a motor is just one kind of engine.
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