Kauai vs island

Kauai and island both are nouns.

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

Kauai (noun)	island (noun)
an island of Hawaii to the northwest of Oahu	a zone or area resembling an island
	a land mass (smaller than a continent) that is surrounded by water