behind vs behindhand

behind is a noun but behindhand is not a noun.

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

As adverbs, behind and behindhand are synonyms defined as:

Other synonyms of behind include in arrears.

behind (noun)	behindhand (noun)
the fleshy part of the human body that you sit on

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

behind (adverb)	behindhand (adverb)
in or to or toward the rear	in debt
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