Pronounced “KAY-luhf.” Successor or representative of the Prophet Muhammad, and the political leader of the Ummah, or Islamic community. A dispute over who should succeed Muhammad after his death prompted the Sunni-Shiite split that continues today. According to Sunnis, who make up the vast majority of Muslims, the first four caliphs were Abu Bakr As-Siddiq, Omar ibn Al-Khattab, Othman ibn ‘Affan and ‘Ali ibn Abi Talib. These four are known collectively as the “Rightly Guided Caliphs.” Shiites believe that Muhammad’s relatives should have succeeded him. Another term for caliph is khalifah.