circumferential vs circumference

circumferential is not a noun while circumference is a noun.

Word	Noun	Adjective	Verb	Adverb
circumferential	No	Yes	No	No
circumference	Yes	No	No	No

circumferential (noun)	circumference (noun)
	the size of something as given by the distance around it
	the length of the closed curve of a circle
	the boundary line encompassing an area or object

circumferential (adjective)	circumference (adjective)
lying around or just outside the edges or outskirts