European Union vs U.K.

European Union and U.K. both are nouns.

Word	Noun	Adjective	Verb	Adverb
European Union	Yes	No	No	No
U.K.	Yes	No	No	No

European Union (noun)	U.K. (noun)
an international organization of European countries formed after World War II to reduce trade barriers and increase cooperation among its members	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