Caliph

The Caliph (Arabic: خليفة‎; /khalīfah/ Turkish: Halife ) is the head of state in a Caliphate, and the title for the leader of the Islamic Ummah, an Islamic community ruled by the Shari'ah. It is a transcribed version of the Arabic word خليفة Khalīfah (help·info)   which means "successor" or "representative". The early leaders of the Muslim nation following Muhammad's (570–632) death were called "Khalifat Rasul Allah", the political successors to the messenger of God (referring to Muhammad). Some academics prefer to transliterate the term as Khalīfah.
Caliphs were often also referred to as Amīr al-Mu'minīn (أمير المؤمنين) "Commander of the Faithful", Imam al-Ummah, Imam al-Mu'minīn (إمام المؤمنين), or more colloquially, leader of the Muslims. After the first four caliphs (Abu Bakr, Umar ibn al-Khattab, Uthman ibn Affan, and Ali ibn Abi Talib), the title was claimed by the Umayyads, the Abbasids, the Fatimids, and the Ottomans, and at times, by competing dynasties in Spain, Northern Africa, and Egypt. Most historical Muslim governors were called sultans or emirs, and gave allegiance to a caliph, but this caliph at times had very little real authority. The title has been defunct since the Republic of Turkey abolished the Ottoman Caliphate in 1924, although some individuals and groups have called for its restoration.^[2] (Hussein bin Ali, Sharif of Mecca and King of Hejaz, claimed the title briefly in 1924, and the Imams of Yemen had been using the title for centuries and continued to use the title until 1962.)