planet gear vs geared wheel

planet gear and geared wheel both are nouns.

Word	Noun	Adjective	Verb	Adverb
planet gear	Yes	No	No	No
geared wheel	Yes	No	No	No

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

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

Other hypernyms of planet gear include cogwheel, gear, gear wheel.

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