Shi'ism is a branch of Islam that developed in the 7th century. It is characterized by a belief in the leadership of the Prophet Muhammad's family, particularly his cousin and son-in-law Ali, over that of the caliphs who succeeded him. Some synonyms for Shi'ism include Shiite Islam, Shia Islam, and Shi'a. These terms are often used interchangeably. Other related terms include Shi'ite, Shiism, and Shiah. While there are some differences between the various branches of Shi'ism, they share common beliefs and practices. Today, Shi'ism is practiced by millions of people around the world, particularly in Iran, Iraq, and Lebanon.
