North vs northern

North is a noun but northern is not a noun.

Word	Noun	Adjective	Verb	Adverb
North	Yes	No	No	No
northern	No	Yes	No	No

North (noun)	northern (noun)
the United States (especially the northern states during the American Civil War)
the region of the United States lying to the north of the Mason-Dixon line
British statesman under George III whose policies led to rebellion in the American colonies (1732-1792)

North (adjective)	northern (adjective)
	situated in regions of the north
	in or characteristic of a region of the United States north of (approximately) the Mason-Dixon line
	coming from the north; used especially of wind
	oriented toward the north