polar circle vs parallel

polar circle and parallel both are nouns.

Word	Noun	Adjective	Verb	Adverb
polar circle	Yes	No	No	No
parallel	Yes	Yes	Yes	No

As nouns, parallel is a hypernym of polar circle; that is, parallel is a word with a broader meaning than polar circle:

Other hypernyms of polar circle include latitude, line of latitude, parallel of latitude.

polar circle (noun)	parallel (noun)
a line of latitude at the north or south poles	something having the property of being analogous to something else
	an imaginary line around the Earth parallel to the equator
	(mathematics) one of a set of parallel geometric figures (parallel lines or planes)

polar circle (adjective)	parallel (adjective)
	being everywhere equidistant and not intersecting
	of or relating to the simultaneous performance of multiple operations

polar circle (verb)	parallel (verb)
	make or place parallel to something
	be parallel to
	duplicate or match