farmer's market vs greenmarket

farmer's market and greenmarket both are nouns.

Word	Noun	Adjective	Verb	Adverb
farmer's market	Yes	No	No	No
greenmarket	Yes	No	No	No

As nouns, farmer's market and greenmarket are synonyms defined as:

farmer's market and greenmarket: an open-air marketplace for farm products

Other synonyms of farmer's market include green market.

farmer's market (noun)	greenmarket (noun)
an open-air marketplace for farm products	an open-air marketplace for farm products