waiting vs inactivity

waiting and inactivity both are nouns.

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

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

waiting: the act of waiting (remaining inactive in one place while expecting something)
inactivity: being inactive; being less active

waiting (noun)	inactivity (noun)
the act of waiting (remaining inactive in one place while expecting something)	being inactive; being less active
	a disposition to remain inactive or inert
	the state of being inactive

waiting (adjective)	inactivity (adjective)
being and remaining ready and available for use