tail end vs behind

tail end and behind both are nouns.

Word	Noun	Adjective	Verb	Adverb
tail end	Yes	No	No	No
behind	Yes	Yes	No	Yes

As nouns, tail end and behind are synonyms defined as:

tail end (noun)	behind (noun)
the fleshy part of the human body that you sit on	the fleshy part of the human body that you sit on
any projection that resembles the tail of an animal
the time of the last part of something

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

tail end (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