Republic of Estonia vs Estonia

Republic of Estonia and Estonia both are nouns.

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

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

Republic of Estonia and Estonia: a republic in northeastern Europe on the Baltic Sea, with capital Tallinn

Other synonyms of Republic of Estonia include Esthonia.

Republic of Estonia (noun)	Estonia (noun)
a republic in northeastern Europe on the Baltic Sea, with capital Tallinn	a republic in northeastern Europe on the Baltic Sea, with capital Tallinn