efficacious vs efficaciousness

efficacious is not a noun while efficaciousness is a noun.

Word	Noun	Adjective	Verb	Adverb
efficacious	No	Yes	No	No
efficaciousness	Yes	No	No	No

efficacious (noun)	efficaciousness (noun)
	capacity or power to produce a desired effect

efficacious (adjective)	efficaciousness (adjective)
marked by qualities giving the power to produce an intended effect
producing or capable of producing an intended result or having a striking effect