North Star vs polestar

North Star and polestar both are nouns.

Word	Noun	Adjective	Verb	Adverb
North Star	Yes	No	No	No
polestar	Yes	No	No	No

As nouns, North Star and polestar are synonyms defined as:

North Star and polestar: the brightest star in Ursa Minor; at the end of the handle of the Little Dipper; the northern axis of the earth points toward it

Other synonyms of North Star include polar star, Polaris, pole star.

North Star (noun)	polestar (noun)
the brightest star in Ursa Minor; at the end of the handle of the Little Dipper; the northern axis of the earth points toward it	the brightest star in Ursa Minor; at the end of the handle of the Little Dipper; the northern axis of the earth points toward it