idleness vs inactivity

idleness and inactivity both are nouns.

Word	Noun	Adjective	Verb	Adverb
idleness	Yes	No	No	No
inactivity	Yes	No	No	No

As nouns, inactivity is a hypernym of idleness; that is, inactivity is a word with a broader meaning than idleness:

idleness (noun)	inactivity (noun)
having no employment	being inactive; being less active
the trait of being idle out of a reluctance to work	a disposition to remain inactive or inert
the quality of lacking substance or value	the state of being inactive