gay vs lesbian

gay and lesbian both are nouns.

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

As nouns, lesbian is a hyponym of gay; that is, lesbian is a word with a more specific, narrower meaning than gay:

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

gay (adjective)	lesbian (adjective)
bright and pleasant; promoting a feeling of cheer	of or relating to or characterized by homosexual relations between woman
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