The minority division within Islam, which consists of at most one-fifth of all Muslims. Shiites are in the majority in Iran (where Shia Islam is the state religion), southern Iraq, and parts of Yemen, and are also found in Syria, Lebanon, East Africa, northern India, and Pakistan. They originated as the Shiat Ali, the ‘party of Ali’, who was the cousin and son-in-law of Muhammad. Ali and his descendants are regarded by Shiites as the only true heirs to Muhammad as leader of the faithful. Shiites now differ from Sunni Muslims in a number of ways but primarily in the importance they attach to the continuing authority of the imams, who are the authentic interpreters of the sunna (customs), the code of conduct based on the Koran and hadith (sayings and deeds of Muhammad). The suffering of the House of the Prophet, chiefly of Husain and his martyrdom in Karbala, and the millenarian expectation of a future imam or Mahdi who is currently hidden from the world, permeate much Shiite thinking, providing a set of beliefs in which oppression and injustice figure largely. The tenth day of the month of Muharram marks the martyrdom of Ali and his sons. Shiites also believe in an inner hidden meaning of the Koran. There are hundreds of different Shiite sects: the main ones are the Zaydis, Ismailis, and Ithna Ashariya (or Twelvers, who await the return of the hidden twelfth imam).