inertia vs restfulness

inertia and restfulness both are nouns.

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

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

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

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