Caliphate
A caliphate (from the Arabic خلافة or khilāfa, Turkish: Hilafet) is a Muslim spiritual community led by a supreme religious (and even political) leader known as a caliph (meaning literally a successor, i.e. a successor to the prophet Mohammad). The term caliphate is often applied to successions of Muslim empires that have existed in the Middle East and Southwest Asia. Conceptually the caliphate represents the political unity of the entire community of Muslim faithful (the ummah) ruled by a single caliph. In theory, the organization of a caliphate should be a constitutional republic (the Constitution being the Constitution of Medina), which means that the head of state, the Caliph, and other officials are representatives of the people and of Islam and must govern according to constitutional and religious law, or Sharia. In its early days, the first caliphate resembled elements of direct democracy (see shura) and an elective monarchy.
Read more about Caliphate.