island vs isle

island and isle both are nouns.

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

As nouns, isle is a hyponym of island; that is, isle is a word with a more specific, narrower meaning than island:

Other hyponyms of island include Caribbean Island, Aegean island, barrier island, islet, South Sea Islands.

island (noun)	isle (noun)
a zone or area resembling an island	a small island
a land mass (smaller than a continent) that is surrounded by water