Fiji vs Republic of Fiji

Fiji and Republic of Fiji both are nouns.

Word	Noun	Adjective	Verb	Adverb
Fiji	Yes	No	No	No
Republic of Fiji	Yes	No	No	No

As nouns, Fiji and Republic of Fiji are synonyms defined as:

Fiji and Republic of Fiji: an independent state within the British Commonwealth located on the Fiji Islands

Fiji (noun)	Republic of Fiji (noun)
an independent state within the British Commonwealth located on the Fiji Islands	an independent state within the British Commonwealth located on the Fiji Islands