nervous vs nervousness

nervous is not a noun while nervousness is a noun.

Word	Noun	Adjective	Verb	Adverb
nervous	No	Yes	No	No
nervousness	Yes	No	No	No

nervous (noun)	nervousness (noun)
	a sensitive or highly strung temperament
	the anxious feeling you have when you have the jitters
	an uneasy psychological state

nervous (adjective)	nervousness (adjective)
of or relating to the nervous system
unpredictably excitable (especially of horses)
excited in anticipation
easily agitated
causing or fraught with or showing anxiety