North Island vs island

North Island and island both are nouns.

Word	Noun	Adjective	Verb	Adverb
North Island	Yes	No	No	No
island	Yes	No	No	No

North Island (noun)	island (noun)
the smaller but more populous of two main islands of New Zealand; separated from South Island by Cook Strait	a zone or area resembling an island
	a land mass (smaller than a continent) that is surrounded by water