The Caliph (Arabic: خليفة‎ ḫalīfah/khalīfah) is the head of state in a Caliphate, and the title for the ruler of the Islamic Ummah, an Islamic community ruled by the Shari'ah. The word derives from the Arabic خليفة Khalīfah, which means "successor" or "representative". Following Muhammad's death in 632, the early leaders of the Muslim nation 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. A Calipha is either a female caliph or the wife or widow of a caliph. There was one known instance in history that a calipha ruled a Caliphate: Sitt al-Mulk was regent of the Fatimid Caliphate from 1221 to 1223. Some caliphas, such as Zaynab an-Nafzawiyyah and Al-Khayzuran bint Atta, wielded great influence in the courts of their husbands.

Read more about Caliph:  Succession To Muhammad, Word Usage, Other Uses, Authority of The Successor, Al-Ghazali On The Desired Character Traits For Administration, Single Caliph For The Muslim World, Notable Caliphs, Dynasties, Claims To The Caliphate