Dublin vs Irish capital

Dublin and Irish capital both are nouns.

Word	Noun	Adjective	Verb	Adverb
Dublin	Yes	No	No	No
Irish capital	Yes	No	No	No

As nouns, Dublin and Irish capital are synonyms defined as:

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

Other synonyms of Dublin include capital of Ireland.

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