pathology vs fistulous

pathology is a noun but fistulous is not a noun.

Word	Noun	Adjective	Verb	Adverb
pathology	Yes	No	No	No
fistulous	No	Yes	No	No

pathology (noun)	fistulous (noun)
the branch of medical science that studies the causes and nature and effects of diseases
any deviation from a healthy or normal condition

pathology (adjective)	fistulous (adjective)
	of or pertaining to or resembling a fistula
	hollow and tube-shaped like a reed