remain vs remainder

remain is not a noun while remainder is a noun.

Word	Noun	Adjective	Verb	Adverb
remain	No	No	Yes	No
remainder	Yes	No	Yes	No

remain (noun)	remainder (noun)
	a piece of cloth that is left over after the rest has been used or sold
	the number that remains after subtraction; the number that when added to the subtrahend gives the minuend
	the part of the dividend that is left over when the dividend is not evenly divisible by the divisor
	something left after other parts have been taken away

remain (verb)	remainder (verb)
stay the same; remain in a certain state	sell cheaply as remainders
be in a certain place and not leave
continue in a place, position, or situation
be left; of persons, questions, problems, results, evidence, etc.