sober vs soberness

sober is not a noun while soberness is a noun.

Word	Noun	Adjective	Verb	Adverb
sober	No	Yes	Yes	No
soberness	Yes	No	No	No

sober (noun)	soberness (noun)
	a manner that is serious and solemn
	the state of being sober and not intoxicated by alcohol

sober (adjective)	soberness (adjective)
not affected by a chemical substance (especially alcohol)
completely lacking in playfulness
lacking brightness or color; dull
dignified and somber in manner or character and committed to keeping promises

sober (verb)	soberness (verb)
become sober after excessive alcohol consumption
become more realistic
cause to become sober