commonness vs uncommon

commonness is a noun but uncommon is not a noun.

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

commonness (noun)	uncommon (noun)
ordinariness as a consequence of being frequent and commonplace
sharing of common attributes
the quality of lacking taste and refinement
the state of being that is commonly observed

commonness (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