Manhattan Island vs island

Manhattan Island and island both are nouns.

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

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