opaque vs opacity

opaque is not a noun while opacity is a noun.

Word	Noun	Adjective	Verb	Adverb
opaque	No	Yes	No	No
opacity	Yes	No	No	No

opaque (noun)	opacity (noun)
	the quality of being opaque to a degree; the degree to which something reduces the passage of light
	incomprehensibility resulting from obscurity of meaning
	the phenomenon of not permitting the passage of electromagnetic radiation

opaque (adjective)	opacity (adjective)
not transmitting or reflecting light or radiant energy; impenetrable to sight
hard or impossible to understand