Eire vs Irish Republic

Eire and Irish Republic both are nouns.

Word	Noun	Adjective	Verb	Adverb
Eire	Yes	No	No	No
Irish Republic	Yes	No	No	No

As nouns, Eire and Irish Republic are synonyms defined as:

Eire and Irish Republic: a republic consisting of 26 of 32 counties comprising the island of Ireland; achieved independence from the United Kingdom in 1921

Other synonyms of Eire include Ireland, Republic of Ireland.

Eire (noun)	Irish Republic (noun)
a republic consisting of 26 of 32 counties comprising the island of Ireland; achieved independence from the United Kingdom in 1921	a republic consisting of 26 of 32 counties comprising the island of Ireland; achieved independence from the United Kingdom in 1921