impassiveness vs impassivity

impassiveness and impassivity both are nouns.

Word	Noun	Adjective	Verb	Adverb
impassiveness	Yes	No	No	No
impassivity	Yes	No	No	No

As nouns, impassiveness and impassivity are synonyms defined as:

impassiveness and impassivity: apathy demonstrated by an absence of emotional reactions

Other synonyms of impassiveness include emotionlessness, indifference, phlegm, stolidity, unemotionality.

impassiveness (noun)	impassivity (noun)
apathy demonstrated by an absence of emotional reactions	apathy demonstrated by an absence of emotional reactions