slender vs slenderness

slender is not a noun while slenderness is a noun.

Word	Noun	Adjective	Verb	Adverb
slender	No	Yes	No	No
slenderness	Yes	No	No	No

slender (noun)	slenderness (noun)
	the quality of being slight or inadequate
	the property of an attractively thin person
	relatively small dimension through an object as opposed to its length or width

slender (adjective)	slenderness (adjective)
very narrow
small in quantity
having little width in proportion to the length or height
being of delicate or slender build