inactivity vs idleness

inactivity and idleness both are nouns.

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

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

Other hyponyms of inactivity include pause, wait, waiting, ease, relaxation, repose, rest, idling, loafing, delay, holdup.

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