laziness vs inertia

laziness and inertia both are nouns.

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

As nouns, inertia is a hypernym of laziness; that is, inertia is a word with a broader meaning than laziness:

Other hypernyms of laziness include inactiveness, inactivity.

laziness (noun)	inertia (noun)
apathy and inactivity in the practice of virtue (personified as one of the deadly sins)	a disposition to remain inactive or inert
relaxed and easy activity	(physics) the tendency of a body to maintain its state of rest or uniform motion unless acted upon by an external force
inactivity resulting from a dislike of work