gambling den vs casino

gambling den and casino both are nouns.

Word	Noun	Adjective	Verb	Adverb
gambling den	Yes	No	No	No
casino	Yes	No	No	No

As nouns, casino is a hyponym of gambling den; that is, casino is a word with a more specific, narrower meaning than gambling den:

gambling den: a public building in which a variety of games of chance can be played (operated as a business)
casino: a public building for gambling and entertainment

Other hyponyms of gambling den include gambling casino.

gambling den (noun)	casino (noun)
a public building in which a variety of games of chance can be played (operated as a business)	a card game in which cards face up on the table are taken with eligible cards in the hand
	a public building for gambling and entertainment