propellor vs mechanical device

propellor and mechanical device both are nouns.

Word	Noun	Adjective	Verb	Adverb
propellor	Yes	No	No	No
mechanical device	Yes	No	No	No

As nouns, mechanical device is a hypernym of propellor; that is, mechanical device is a word with a broader meaning than propellor:

propellor: a mechanical device that rotates to push against air or water
mechanical device: mechanism consisting of a device that works on mechanical principles

propellor (noun)	mechanical device (noun)
a mechanical device that rotates to push against air or water	mechanism consisting of a device that works on mechanical principles