monopoly vs marketplace

monopoly and marketplace both are nouns.

Word	Noun	Adjective	Verb	Adverb
monopoly	Yes	No	No	No
marketplace	Yes	No	No	No

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

monopoly: (economics) a market in which there are many buyers but only one seller
marketplace: the world of commercial activity where goods and services are bought and sold

Other hypernyms of monopoly include market, market place.

monopoly (noun)	marketplace (noun)
(economics) a market in which there are many buyers but only one seller	the world of commercial activity where goods and services are bought and sold
exclusive control or possession of something	an area in a town where a public mercantile establishment is set up