Kingdom of Belgium vs Belgium

Kingdom of Belgium and Belgium both are nouns.

Word	Noun	Adjective	Verb	Adverb
Kingdom of Belgium	Yes	No	No	No
Belgium	Yes	No	No	No

As nouns, Kingdom of Belgium and Belgium are synonyms defined as:

Kingdom of Belgium and Belgium: a monarchy in northwestern Europe; headquarters for the European Union and for the North Atlantic Treaty Organization

Other synonyms of Kingdom of Belgium include Belgique.

Kingdom of Belgium (noun)	Belgium (noun)
a monarchy in northwestern Europe; headquarters for the European Union and for the North Atlantic Treaty Organization	a monarchy in northwestern Europe; headquarters for the European Union and for the North Atlantic Treaty Organization