tangent vs tangential

tangent is a noun but tangential is not a noun.

Word	Noun	Adjective	Verb	Adverb
tangent	Yes	No	No	No
tangential	No	Yes	No	No

tangent (noun)	tangential (noun)
ratio of the opposite to the adjacent side of a right-angled triangle
a straight line or plane that touches a curve or curved surface at a point but does not intersect it at that point

tangent (adjective)	tangential (adjective)
	of or relating to or acting along or in the direction of a tangent
	of superficial relevance if any