Federation
A federation, or federal state is an entity characterized by a union of partially self-governing provinces, states, or other regions under a 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 constitutionally entrenched and may not be altered by a unilateral decision, neither by the component states nor the federal political body without constitutional amendment. A federation is in contrast to a unitary state.