Islam in the Ottoman Empire
Islam was the official religion of the Ottoman Empire. The highest position in Islam, "caliphate", was claimed by the sultan, after the defeat of the Mamluks which was established as Ottoman Caliphate. The Sultan was to be a devout Muslim and was given the literal authority of the Caliph. Additionally, Sunni clerics had tremendous influence over government and their authority was central to the regulation of the economy. Despite all this, the Sultan also had a right to decree, enforcing a code called Kanun (law) in Turkish. Additionally, there was a supreme clerical position called the Sheykhulislam ("Sheykh of Islam" in Arabic). Minorities, particularly Christians and Jews but also some others, were mandated to pay the jizya, the poll tax as mandated by traditional Islam.
Janina Vilayet
There have been a number of estimates about the ethnicity and the religious affiliation of the local population. The Ottoman Empire classified and counted its citizens according to religion and not ethnicity, which led to inefficient censuses and lack of classification of populations according to their ethnic groups. The vilayet was predominantly inhabited by Albanians and Greeks, while the major religions were Islam and Christian Orthodoxy. The vilayet was heavily Greek, especially the part that would be later incorporated to Greece.