inactiveness vs phlegm

inactiveness and phlegm both are nouns.

Word	Noun	Adjective	Verb	Adverb
inactiveness	Yes	No	No	No
phlegm	Yes	No	No	No

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

Other hyponyms of inactiveness include flatness, languor, lethargy, sluggishness, restfulness, passiveness, passivity, indolence, laziness.

inactiveness (noun)	phlegm (noun)
a disposition to remain inactive or inert	inactivity; showing an unusual lack of energy
the state of being inactive	expectorated matter; saliva mixed with discharges from the respiratory passages; in ancient and medieval physiology it was believed to cause sluggishness
	apathy demonstrated by an absence of emotional reactions