sex vs rear end

sex and rear end both are nouns.

Word	Noun	Adjective	Verb	Adverb
sex	Yes	No	Yes	No
rear end	Yes	No	No	No

sex (noun)	rear end (noun)
activities associated with sexual intercourse	the fleshy part of the human body that you sit on
the properties that distinguish organisms on the basis of their reproductive roles
all of the feelings resulting from the urge to gratify sexual impulses
either of the two categories (male or female) into which most organisms are divided

sex (verb)	rear end (verb)
tell the sex (of young chickens)
to evoke sexual feelings