polyvalent vs valency

polyvalent is not a noun while valency is a noun.

Word	Noun	Adjective	Verb	Adverb
polyvalent	No	Yes	No	No
valency	Yes	No	No	No

polyvalent (noun)	valency (noun)
	(chemistry) a property of atoms or radicals; their combining power given in terms of the number of hydrogen atoms (or the equivalent)
	(biology) a relative capacity to unite or react or interact as with antigens or a biological substrate
	the phenomenon of forming chemical bonds

polyvalent (adjective)	valency (adjective)
having more than one valence, or having a valence of 3 or higher
containing several antibodies each capable of counteracting a specific antigen