commonplaceness vs uncommon

commonplaceness is a noun but uncommon is not a noun.

Word	Noun	Adjective	Verb	Adverb
commonplaceness	Yes	No	No	No
uncommon	No	Yes	No	No

commonplaceness (noun)	uncommon (noun)
ordinariness as a consequence of being frequent and commonplace

commonplaceness (adjective)	uncommon (adjective)
	not common or ordinarily encountered; unusually great in amount or remarkable in character or kind
	marked by an uncommon quality; especially superlative or extreme of its kind