planetary gear vs epicyclic gear

planetary gear and epicyclic gear both are nouns.

Word	Noun	Adjective	Verb	Adverb
planetary gear	Yes	No	No	No
epicyclic gear	Yes	No	No	No

As nouns, planetary gear and epicyclic gear are synonyms defined as:

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

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

planetary gear (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