<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> A federation (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, is typically constitutionally entrenched and may not be altered by a unilateral decision of either party, the states or the federal political body . Alternatively, federation is a form of government in which sovereign power is formally divided between a central authority and a number of constituent regions so that each region retains some degree of control over its internal affairs . </P> <P> The governmental or constitutional structure found in a federation is considered to be federalist, or to be an example of federalism . It can be considered the opposite of another system, the unitary state . France, for example, has always been unitary . Neighboring Austria and its Bundesländer was a unitary state with administrative divisions that became federated through the implementation of the Austrian Constitution following the 1918 collapse of Austria - Hungary . Germany, with its 16 states or Bundesländer, is an example of a federation . </P>

What is the main feature of a federation