sluggish vs sluggishness

sluggish is not a noun while sluggishness is a noun.

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

sluggish (noun)	sluggishness (noun)
	inactivity; showing an unusual lack of energy
	the pace of things that move relatively slowly
	a state of comatose torpor (as found in sleeping sickness)

sluggish (adjective)	sluggishness (adjective)
slow and apathetic
(of business) not active or brisk
slow or slothful