A national trade union center (or national center or central) is a federation or confederation of trade unions in a single country.[1] Nearly every country in the world has a national trade union center, and many have more than one. When there is more than one national center, it is often because of ideological differences—in some cases long-standing historic differences. In some regions, such as the Nordic countries, different centers exist on a sectoral basis, for example for blue collar workers and professionals.