mirthful vs gay

mirthful is not a noun while gay is a noun.

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

As adjectives, mirthful and gay are synonyms defined as:

Other synonyms of mirthful include jocund, jolly, jovial, merry.

mirthful (noun)	gay (noun)
	someone who is sexually attracted to persons of the same sex

mirthful (adjective)	gay (adjective)
arousing or provoking laughter	bright and pleasant; promoting a feeling of cheer
full of or showing high-spirited merriment	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