polar region vs Frigid Zone

polar region and Frigid Zone both are nouns.

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

As nouns, polar region and Frigid Zone are synonyms defined as:

polar region and Frigid Zone: the part of the Earth's surface forming a cap over a pole; characterized by frigid climate

Other synonyms of polar region include polar zone.

polar region (noun)	Frigid Zone (noun)
the part of the Earth's surface forming a cap over a pole; characterized by frigid climate	the part of the Earth's surface forming a cap over a pole; characterized by frigid climate