epicyclic gear vs planet wheel

epicyclic gear and planet wheel both are nouns.

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

As nouns, epicyclic gear and planet wheel are synonyms defined as:

epicyclic gear and planet wheel: an outer gear that revolves about a central sun gear of an epicyclic train

Other synonyms of epicyclic gear include planet gear, planetary gear.

epicyclic gear (noun)	planet wheel (noun)
an outer gear that revolves about a central sun gear of an epicyclic train	an outer gear that revolves about a central sun gear of an epicyclic train