open-air marketplace vs open-air market

open-air marketplace and open-air market both are nouns.

Word	Noun	Adjective	Verb	Adverb
open-air marketplace	Yes	No	No	No
open-air market	Yes	No	No	No

As nouns, open-air marketplace and open-air market are synonyms defined as:

open-air marketplace and open-air market: a public marketplace where food and merchandise is sold

Other synonyms of open-air marketplace include market square.

open-air marketplace (noun)	open-air market (noun)
a public marketplace where food and merchandise is sold	a public marketplace where food and merchandise is sold