European Union vs Common Market

European Union and Common Market both are nouns.

Word	Noun	Adjective	Verb	Adverb
European Union	Yes	No	No	No
Common Market	Yes	No	No	No

As nouns, European Union and Common Market are synonyms defined as:

European Union and Common Market: an international organization of European countries formed after World War II to reduce trade barriers and increase cooperation among its members

Other synonyms of European Union include EC, EEC, EU, Europe, European Community, European Economic Community.

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