gay man vs gay

gay man and gay both are nouns.

Word	Noun	Adjective	Verb	Adverb
gay man	Yes	No	No	No
gay	Yes	Yes	No	No

As nouns, gay is a hypernym of gay man; that is, gay is a word with a broader meaning than gay man:

Other hypernyms of gay man include homo, homophile, homosexual, adult male, man.

gay man (noun)	gay (noun)
a homosexual man	someone who is sexually attracted to persons of the same sex

gay man (adjective)	gay (adjective)
	bright and pleasant; promoting a feeling of cheer
	brightly colored and showy
	homosexual or arousing homosexual desires
	given to social pleasures often including dissipation
	offering fun and gaiety
	full of or showing high-spirited merriment