market square vs marketplace

market square and marketplace both are nouns.

Word	Noun	Adjective	Verb	Adverb
market square	Yes	No	No	No
marketplace	Yes	No	No	No

As nouns, marketplace is a hypernym of market square; that is, marketplace is a word with a broader meaning than market square:

market square: a public marketplace where food and merchandise is sold
marketplace: an area in a town where a public mercantile establishment is set up

Other hypernyms of market square include market, market place, mart.

market square (noun)	marketplace (noun)
a public marketplace where food and merchandise is sold	the world of commercial activity where goods and services are bought and sold
	an area in a town where a public mercantile establishment is set up