Federation

A federation, also called a federal state, is a union of partially self-governing provinces, states or other regions under a federal government. The cited article explains that the self-governing status of the component units and the division of power between them and the central government are constitutionally entrenched, so neither side may alter them unilaterally without following the constitutional amendment process, and that sovereign power is formally divided between a central authority and a number of constituent regions, each keeping some control over its internal affairs. The structure is commonly contrasted with the unitary state; France and Japan are given as unitary examples, while Germany with its sixteen states and Nigeria with thirty-six states and a federal capital territory are given as federations. Roughly 40 per cent of the world's population lives in countries described as federal.