Ireland vs Emerald Isle

Ireland and Emerald Isle both are nouns.

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

As nouns, Ireland and Emerald Isle are synonyms defined as:

Ireland and Emerald Isle: an island comprising the republic of Ireland and Northern Ireland

Other synonyms of Ireland include Hibernia.

Ireland (noun)	Emerald Isle (noun)
an island comprising the republic of Ireland and Northern Ireland	an island comprising the republic of Ireland and Northern Ireland
a republic consisting of 26 of 32 counties comprising the island of Ireland; achieved independence from the United Kingdom in 1921