Republic of Cuba vs Cuba

Republic of Cuba and Cuba both are nouns.

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

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

Republic of Cuba and Cuba: a communist state in the Caribbean on the island of Cuba

Republic of Cuba (noun)	Cuba (noun)
a communist state in the Caribbean on the island of Cuba	a communist state in the Caribbean on the island of Cuba
	the largest island in the West Indies