Caliph is the term or title for the Islamic leader of the Ummah, or community of Islam. It is an Anglicized/Latinized version of the Arabic word خليفة or Khalīfah, which means "successor", that is, successor to the Muhammad. Some Orientalists wrote the title as Khalîf. The Caliph has often been referred to as Ameer al-Mumineen (أمير المؤمنين), or "Prince of the Faithful," where "Prince" is used in the context of "commander." The title has been defunct since the abolition of the Ottoman Sultanate in 1924.

Ayatollah

Ayatollah (Arabic: آية الله; Persian: آیت‌الله) is a high title given to major Shia clergymen. The word means 'sign of God', and those who carry the title are experts in Islamic studies such as jurisprudence, ethics, philosophy and mysticism, and usually teach in schools (hawza) of Islamic sciences. Ayatollahs can reach the position of a Marja-e-Taqlid, which allows them to issue fatāwi (Arabic, plural of "fatwa"). Also see The Grand Ayatollah.

Mullah or Mawlana

Mullah or Mawlana are Islamic clergy who have studied the Qur'an and the Hadith and are considered experts on related religious matters in this religion. The term Mullah is a variation of the word mawla(means master or lord) and Mawlana is its derivative (means my lord) and are used mainly in Central Asia and in the Sub-Continent .