epicyclic gear vs planetary gear

epicyclic gear and planetary gear both are nouns.

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

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

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

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

epicyclic gear (noun)	planetary 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