inertia vs inactiveness

inertia and inactiveness both are nouns.

Word	Noun	Adjective	Verb	Adverb
inertia	Yes	No	No	No
inactiveness	Yes	No	No	No

As nouns, inertia and inactiveness are synonyms defined as:

Other synonyms of inertia include inactivity.

inertia (noun)	inactiveness (noun)
a disposition to remain inactive or inert	a disposition to remain inactive or inert
(physics) the tendency of a body to maintain its state of rest or uniform motion unless acted upon by an external force	the state of being inactive