fiber vs fibrous

fiber is a noun but fibrous is not a noun.

Word	Noun	Adjective	Verb	Adverb
fiber	Yes	No	No	No
fibrous	No	Yes	No	No

fiber (noun)	fibrous (noun)
a leatherlike material made by compressing layers of paper or cloth
the inherent complex of attributes that determines a persons moral and ethical actions and reactions
any of several elongated, threadlike cells (especially a muscle fiber or a nerve fiber)
coarse, indigestible plant food low in nutrients; its bulk stimulates intestinal peristalsis
a slender and greatly elongated substance capable of being spun into yarn

fiber (adjective)	fibrous (adjective)
	(of meat) full of sinews; especially impossible to chew
	having or resembling fibers especially fibers used in making cordage such as those of jute