Benin vs Republic of Benin

Benin and Republic of Benin both are nouns.

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

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

Benin and Republic of Benin: a country on western coast of Africa; formerly under French control

Other synonyms of Benin include Dahomey.

Benin (noun)	Republic of Benin (noun)
a country on western coast of Africa; formerly under French control	a country on western coast of Africa; formerly under French control