kitchen island vs island

kitchen island and island both are nouns.

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

As nouns, island is a hypernym of kitchen island; that is, island is a word with a broader meaning than kitchen island:

kitchen island: an unattached counter in a kitchen that permits access from all sides
island: a zone or area resembling an island

kitchen island (noun)	island (noun)
an unattached counter in a kitchen that permits access from all sides	a zone or area resembling an island
	a land mass (smaller than a continent) that is surrounded by water