polar region vs North Frigid Zone

polar region and North Frigid Zone both are nouns.

Word	Noun	Adjective	Verb	Adverb
polar region	Yes	No	No	No
North Frigid Zone	Yes	No	No	No

polar region (noun)	North Frigid Zone (noun)
the part of the Earth's surface forming a cap over a pole; characterized by frigid climate	the regions to the north of the Arctic Circle centered on the North Pole