spur gear vs gear wheel

spur gear and gear wheel both are nouns.

Word	Noun	Adjective	Verb	Adverb
spur gear	Yes	No	No	No
gear wheel	Yes	No	No	No

As nouns, gear wheel is a hypernym of spur gear; that is, gear wheel is a word with a broader meaning than spur gear:

spur gear: gear wheels that mesh in the same plane
gear wheel: a toothed wheel that engages another toothed mechanism in order to change the speed or direction of transmitted motion

Other hypernyms of spur gear include cogwheel, gear, geared wheel.

spur gear (noun)	gear wheel (noun)
gear wheels that mesh in the same plane	a toothed wheel that engages another toothed mechanism in order to change the speed or direction of transmitted motion