, 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.