sleep together vs love

sleep together is not a noun while love is a noun.

Word	Noun	Adjective	Verb	Adverb
sleep together	No	No	Yes	No
love	Yes	No	Yes	No

As verbs, sleep together and love are synonyms defined as:

sleep together (noun)	love (noun)
	sexual activities (often including sexual intercourse) between two people
	any object of warm affection or devotion
	a strong positive emotion of regard and affection
	a deep feeling of sexual desire and attraction
	a beloved person; used as terms of endearment
	a score of zero in tennis or squash

sleep together (verb)	love (verb)
have sexual intercourse with	have sexual intercourse with
	have a great affection or liking for
	be enamored or in love with
	get pleasure from