Supra-nationality
"Supra" means "above" - in this case "above the nations".
As a member of the EU, a state gives up its sovereignty to the supra-national EU. Thus, a country can no longer decide various domestic and international policies on its own.
The EU voting systems can mean that if a majority of members in the EU adopt a law it will also come into force in countries that voted against it. In this way the national parliaments have transferred some of their powers (competence) to the EU institutions.
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See also Primacy.