Niihau vs island

Niihau and island both are nouns.

Word	Noun	Adjective	Verb	Adverb
Niihau	Yes	No	No	No
island	Yes	No	No	No

Niihau (noun)	island (noun)
the most northwestern Hawaiian island (beyond Kauai)	a zone or area resembling an island
	a land mass (smaller than a continent) that is surrounded by water