sleep together vs neck

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

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

sleep together (noun)	neck (noun)
	an opening in a garment for the neck of the wearer; a part of the garment near the wearer's neck
	a narrow part of an artifact that resembles a neck in position or form
	the part of an organism (human or animal) that connects the head to the rest of the body
	a cut of meat from the neck of an animal
	a narrow elongated projecting strip of land

sleep together (verb)	neck (verb)
have sexual intercourse with	kiss, embrace, or fondle with sexual passion