European Union vs Great Britain

European Union and Great Britain both are nouns.

Word	Noun	Adjective	Verb	Adverb
European Union	Yes	No	No	No
Great Britain	Yes	No	No	No

European Union (noun)	Great Britain (noun)
an international organization of European countries formed after World War II to reduce trade barriers and increase cooperation among its members	an island comprising England and Scotland and Wales
	a monarchy in northwestern Europe occupying most of the British Isles; divided into England and Scotland and Wales and Northern Ireland; `Great Britain' is often used loosely to refer to the United Kingdom