island vs Manhattan Island

island and Manhattan Island both are nouns.

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

island (noun)	Manhattan Island (noun)
a zone or area resembling an island	an island at the north end of New York Bay where the borough of Manhattan is located
a land mass (smaller than a continent) that is surrounded by water