sluggishness vs inactivity

sluggishness and inactivity both are nouns.

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

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

Other hypernyms of sluggishness include inactiveness, inertia.

sluggishness (noun)	inactivity (noun)
inactivity; showing an unusual lack of energy	being inactive; being less active
the pace of things that move relatively slowly	a disposition to remain inactive or inert
a state of comatose torpor (as found in sleeping sickness)	the state of being inactive