inertia vs passiveness

inertia and passiveness both are nouns.

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

As nouns, passiveness is a hyponym of inertia; that is, passiveness is a word with a more specific, narrower meaning than inertia:

Other hyponyms of inertia include flatness, languor, lethargy, phlegm, sluggishness, restfulness, passivity, indolence, laziness.

inertia (noun)	passiveness (noun)
a disposition to remain inactive or inert	the trait of remaining inactive; a lack of initiative
(physics) the tendency of a body to maintain its state of rest or uniform motion unless acted upon by an external force	submission to others or to outside influences