spur gear vs cogwheel

spur gear and cogwheel both are nouns.

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

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

spur gear: gear wheels that mesh in the same plane
cogwheel: 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 gear, gear wheel, geared wheel.

spur gear (noun)	cogwheel (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