Dublin vs capital of Ireland

Dublin and capital of Ireland both are nouns.

Word	Noun	Adjective	Verb	Adverb
Dublin	Yes	No	No	No
capital of Ireland	Yes	No	No	No

As nouns, Dublin and capital of Ireland are synonyms defined as:

Dublin and capital of Ireland: capital and largest city and major port of the Irish Republic

Other synonyms of Dublin include Irish capital.

Dublin (noun)	capital of Ireland (noun)
capital and largest city and major port of the Irish Republic	capital and largest city and major port of the Irish Republic