circumference vs boundary line

circumference and boundary line both are nouns.

Word	Noun	Adjective	Verb	Adverb
circumference	Yes	No	No	No
boundary line	Yes	No	No	No

As nouns, boundary line is a hypernym of circumference; that is, boundary line is a word with a broader meaning than circumference:

Other hypernyms of circumference include border, borderline, delimitation, mete.

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