sexual activity vs behind

sexual activity and behind both are nouns.

Word	Noun	Adjective	Verb	Adverb
sexual activity	Yes	No	No	No
behind	Yes	Yes	No	Yes

sexual activity (noun)	behind (noun)
activities associated with sexual intercourse	the fleshy part of the human body that you sit on

sexual activity (adjective)	behind (adjective)
	having the lower score or lagging position in a contest

sexual activity (adverb)	behind (adverb)
	in or to or toward the rear
	remaining in a place or condition that has been left or departed from
	in debt
	in or into an inferior position
	showing a time that is earlier than the actual time