screw propeller vs propellor

screw propeller and propellor both are nouns.

Word	Noun	Adjective	Verb	Adverb
screw propeller	Yes	No	No	No
propellor	Yes	No	No	No

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

screw propeller: a propeller with several angled blades that rotates to push against water or air
propellor: a mechanical device that rotates to push against air or water

Other hypernyms of screw propeller include propeller.

screw propeller (noun)	propellor (noun)
a propeller with several angled blades that rotates to push against water or air	a mechanical device that rotates to push against air or water