What is an “engine”?

by Jason Crawford · April 8, 2017 · 1 min read

Reading about the original steam engines raised a question for me: What did the term “engine” even mean before the steam engine?

The first steam engine was called an “engine”, so the word was around and it meant something. And I knew the term “siege engine”, which I guess refers to catapults and things. But today the term mostly refers to something that takes fuel and combusts it somehow to generate motion, usually turning a shaft of some kind. What did it mean before any such invention existed?

Wikipedia confirms my understanding of the contemporary meaning of the term:

In modern usage, the term engine typically describes devices, like steam engines and internal combustion engines, that burn or otherwise consume fuel to perform mechanical work by exerting a torque or linear force (usually in the form of thrust). Devices converting heat energy into motion are commonly referred to simply as engines. Examples of engines which exert a torque include the familiar automobile gasoline and diesel engines, as well as turboshafts. Examples of engines which produce thrust include turbofans and rockets.

Reading the rest of that page, it seems that the term originally referred to any (complex?) mechanical device that took any form of energy and converted it into useful mechanical motion. So something hooked up to a wind or water mill, or even powered by humans or animals, would be called an engine.

It’s interesting to me that the very meaning of the term has changed, and it underscores the dramatic significance of the invention.