ass vs behind

ass and behind both are nouns.

Word	Noun	Adjective	Verb	Adverb
ass	Yes	No	No	No
behind	Yes	Yes	No	Yes

As nouns, ass and behind are synonyms defined as:

ass (noun)	behind (noun)
slang for sexual intercourse	the fleshy part of the human body that you sit on
hardy and sure-footed animal smaller and with longer ears than the horse
the fleshy part of the human body that you sit on
a pompous fool

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

ass (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