complaint vs complain

complaint is a noun but complain is not a noun.

Word	Noun	Adjective	Verb	Adverb
complaint	Yes	No	No	No
complain	No	No	Yes	No

complaint (noun)	complain (noun)
an expression of grievance or resentment
(formerly) a loud cry (or repeated cries) of pain or rage or sorrow
(civil law) the first pleading of the plaintiff setting out the facts on which the claim for relief is based
(criminal law) a pleading describing some wrong or offense
an often persistent bodily disorder or disease; a cause for complaining

complaint (verb)	complain (verb)
	express complaints, discontent, displeasure, or unhappiness
	make a formal accusation; bring a formal charge