public square vs mart

public square and mart both are nouns.

Word	Noun	Adjective	Verb	Adverb
public square	Yes	No	No	No
mart	Yes	No	No	No

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

Other hypernyms of public square include market, market place, marketplace.

public square (noun)	mart (noun)
a place of assembly for the people in ancient Greece	an area in a town where a public mercantile establishment is set up
an open area at the meeting of two or more streets