effectiveness vs effectivity

effectiveness and effectivity both are nouns.

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

As nouns, effectiveness and effectivity are synonyms defined as:

effectiveness and effectivity: power to be effective; the quality of being able to bring about an effect

Other synonyms of effectiveness include effectuality, effectualness.

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