nervousness vs nervous

nervousness is a noun but nervous is not a noun.

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

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

nervousness (adjective)	nervous (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