A federal system is a form of government in which power is shared between a central government and individual states or regions. Synonyms for a federal system include a federation, confederation, decentralized system, or a union of states. The term "federalism" is often used interchangeably with a federal system to describe this type of government structure. Other related terms include devolution, which refers to the transfer of power from a central government to local or regional governments, and subsidiarity, which suggests that decisions should be made at the lowest level of government possible. Overall, the concept of federalism is an important aspect of many nations' political systems.