phlegm vs impassiveness

phlegm and impassiveness both are nouns.

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

As nouns, phlegm and impassiveness are synonyms defined as:

phlegm and impassiveness: apathy demonstrated by an absence of emotional reactions

Other synonyms of phlegm include emotionlessness, impassivity, indifference, stolidity, unemotionality.

phlegm (noun)	impassiveness (noun)
inactivity; showing an unusual lack of energy	apathy demonstrated by an absence of emotional reactions
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