sun gear vs cogwheel

sun gear and cogwheel both are nouns.

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

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

sun gear: the central gear in an epicyclic train
cogwheel: a toothed wheel that engages another toothed mechanism in order to change the speed or direction of transmitted motion

Other hypernyms of sun gear include gear, gear wheel, geared wheel.

sun gear (noun)	cogwheel (noun)
the central gear in an epicyclic train	a toothed wheel that engages another toothed mechanism in order to change the speed or direction of transmitted motion