Caliph is a title granted to those considered to be a political-religious successors of Muhammad; any political structure run by a caliph is a caliphate. The first four caliphs were the Rashidun, Muhammad’s immediate successors who knew him personally and who sought to continue his political and religious missions as had been personally relayed to them. Following the schism between Sunni and Shia Islam, Muslims around the world have continuously disagreed about who is a rightful caliph. Nevertheless, Sunni polities like the Umayyad Empire are recognized by historians as a caliphate, and are referred to as such throughout Islam: A Short History.

“Dhimmi” is a term used in premodern Muslim empires to describe non-Muslims who were afforded protected status by the government. These groups included Hindus, Buddhists, Zoroastrians, Sikhs, Jews, and Christians. Muslim governments granted dhimmis complete religious liberty so long as they recognized Islamic political authority. Armstrong emphasizes the relatively peaceful relationship between dhimmis and their Muslim governments (as opposed to Jewish and Muslim minority groups who faced persecution when living under Christian rule) to counteract modern Western stereotypes that portray Islam as an inherently intolerant religion.