efficacy vs effectiveness

efficacy and effectiveness both are nouns.

Word	Noun	Adjective	Verb	Adverb
efficacy	Yes	No	No	No
effectiveness	Yes	No	No	No

As nouns, effectiveness is a hypernym of efficacy; that is, effectiveness is a word with a broader meaning than efficacy:

efficacy: capacity or power to produce a desired effect
effectiveness: power to be effective; the quality of being able to bring about an effect

Other hypernyms of efficacy include effectivity, effectuality, effectualness.

efficacy (noun)	effectiveness (noun)
capacity or power to produce a desired effect	power to be effective; the quality of being able to bring about an effect
	capacity to produce strong physiological or chemical effects