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'.
1: https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi...
2: https://www.apogeerockets.com/bmz_cache/f/f8ecac9604d017a5c7...
3: https://estesrockets.com/products/b6-4-engines
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'.
1: https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi...
2: https://www.apogeerockets.com/bmz_cache/f/f8ecac9604d017a5c7...
3: https://estesrockets.com/products/b6-4-engines