restrainer vs restrain

restrainer is a noun but restrain is not a noun.

Word	Noun	Adjective	Verb	Adverb
restrainer	Yes	No	No	No
restrain	No	No	Yes	No

restrainer (noun)	restrain (noun)
a person who directs and restrains
a chemical that is added to a photographic developer in order to retard development and reduce the amount of fog on a film

restrainer (verb)	restrain (verb)
	prevent the action or expression of
	to close within bounds, or otherwise limit or deprive of free movement
	restrict (someone or something) so as to make free movement difficult
	prevent (someone or something) from doing something