numb vs numbness

numb is not a noun while numbness is a noun.

Word	Noun	Adjective	Verb	Adverb
numb	No	Yes	Yes	No
numbness	Yes	No	No	No

numb (noun)	numbness (noun)
	the trait of lacking enthusiasm for or interest in things generally
	partial or total lack of sensation in a part of the body; a symptom of nerve damage or dysfunction

numb (adjective)	numbness (adjective)
so frightened as to be unable to move; stunned or paralyzed with terror; petrified
lacking sensation
(followed by `to') not showing human feeling or sensitivity; unresponsive

numb (verb)	numbness (verb)
make numb or insensitive