A state in which constitutional authority is divided between a national government and constituent units (states, provinces, cantons or Länder), each holding powers the other cannot unilaterally remove.
In more detail
Germany's Basic Law describes the country as a federal state, and its Article 79(3) bars amendments that abolish the division into Länder. Switzerland's constitution treats the cantons as sovereign except where limited by the federal constitution. Federations vary between dual models, with separate spheres, and cooperative ones, with shared tasks. Riker argued that federations arise from bargains to meet shared threats.