planet wheel vs epicyclic gear

planet wheel and epicyclic gear both are nouns.

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

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

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

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

planet wheel (noun)	epicyclic gear (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