ELI5: What is the distinction between an engine and a motor?

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The word “motor” literally means “mover” in latin and originally meant any device which caused things to move. The word “engine” has the same origin as “ingenuity” and originally just meant any technological device. Today I think it implies a device or system designed to run continuously (a mousetrap would not be referred to as an engine but a game kernel would be). Outside of computing and theoretical science, engine is used almost exclusively to refer to motors. Obviously there’s a lot of overlap between those definitions and they blurred together to the point that there’s no difference in normal conversation. The times that we distinguish are 1) where the engines are not explicitly motors (“heat engine”, “game engine”, “difference engine”) 2) Simple, one shot motors (clockwork/rubber band motors, solid fuel rocket motors, etc)


Don’t overthink this. Neither are technical terms with hard and fast meaning. An engine is something that converts energy to do work. So you have steam engines, internal combustion engines, but you also have the cotton engine (cotton gin) and seige engines (catapult, trebuchet), and Babbage’s engine, an early calculator. The word motor was initially used to refer to internal combustion engines, to differentiate them from steam engines. But you have electric motors and rocket motors and even motor proteins.


Classically; engines are motors, but motors are not necessarily engines. Engines would commonly signify that; 1) The motor converts heat into kinetic energy, and; 2) The motor accomplishes this conversion via a reciprocating motion of some kind (so as to differentiate from turbines). By comparison, a motor is just something that produces rotational kinetic energy from some process (i.e. it spins a shaft, but it doesn’t strictly matter how). In *modern* usage; motors are going to be shorthand for ***electric*** motors, i.e. the rotational motion is driven by electrical energy.


An engine is a prime mover, it takes fuel and converts it to motion. Chemical to mechanical / kinetic. A motor is a secondary mover, it converts one type of energy to another, electrical to kinetic for example. You have hydraulic motors and pneumatic motors.


They way I was told is that motors use some sort of outside power. Like electricity or hydraulic pressure where as an engine “makes its own power?” I’m not sure if that makes sense but the engine can run on its own and the motor can’t