island vs Emerald Isle

island and Emerald Isle both are nouns.

Word	Noun	Adjective	Verb	Adverb
island	Yes	No	No	No
Emerald Isle	Yes	No	No	No

island (noun)	Emerald Isle (noun)
a zone or area resembling an island	an island comprising the republic of Ireland and Northern Ireland
a land mass (smaller than a continent) that is surrounded by water