remissness vs slackness

remissness and slackness both are nouns.

Word	Noun	Adjective	Verb	Adverb
remissness	Yes	No	No	No
slackness	Yes	No	No	No

As nouns, remissness and slackness are synonyms defined as:

Other synonyms of remissness include laxity, laxness.

remissness (noun)	slackness (noun)
the quality of being lax and neglectful	the quality of being loose (not taut)
	the quality of being lax and neglectful
	weakness characterized by a lack of vitality or energy