sluggishness vs phlegm

sluggishness and phlegm both are nouns.

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

As nouns, sluggishness and phlegm are synonyms defined as:

Other synonyms of sluggishness include flatness, languor, lethargy.

sluggishness (noun)	phlegm (noun)
inactivity; showing an unusual lack of energy	inactivity; showing an unusual lack of energy
the pace of things that move relatively slowly	expectorated matter; saliva mixed with discharges from the respiratory passages; in ancient and medieval physiology it was believed to cause sluggishness
a state of comatose torpor (as found in sleeping sickness)	apathy demonstrated by an absence of emotional reactions