Federation

A federation (from Latin: foedus, gen.: foederis, "covenant"), also known as a federal state, is a political entity characterized by a union of partially self-governing states or regions under a central (federal) government. In a federation, the self-governing status of the component states, as well as the division of power between them and the central government, are typically constitutionally entrenched and may not be altered by a unilateral decision of either party, the states or the federal political body.

The governmental or constitutional structure found in a federation is known as federalism. It can be considered the opposite of another system, the unitary state. Germany, with sixteen Bundesländer, is an example of a federation, whereas neighboring Austria and its Bundesländer was a unitary state with administrative divisions that became federated, and neighboring France by contrast has always been unitary.

Federations may be multi-ethnic and cover a large area of territory (e.g. Russia, the United States, or India), although neither is necessarily the case. The initial agreements create a stability that encourages other common interests, reduces differences between the disparate territories, and gives them all even more common ground. At some time this is recognized and a movement is organized to merge more closely. At other times, especially when common cultural factors are at play such as ethnicity and language, some of the steps in this pattern are expedited and compressed.