An imam is a person having great authority in Islam. There are five different specific meanings of the term:
- in a mosque, a leader in prayer is the imam only while he leads the prayer. More generally, the imam is the most respected person in the assembly. In modern times, the term has expanded to include a leader employed by the congregation, like a priest in Christianity.
- in Shia Islam, the highest leader is the imam. The first imam was Ali. The imam is presumed to have a special relationship to Allah.
- Under the direction of Ayatollah Khomeini in Shia Islam, the imam alone was no longer considered to be the sole leader and authority, and Khomeini and his associates ruled the religious life in Iran.
- In the largest branch of Islam, Sunni Islam, caliphs were called imams. But there are no longer any caliphs, so the term "imam" in that sense means almost nothing today.
- Also in Sunni Islam, "imam" is added to the names of learned men, such as founders of the schools of Sharia and as an honor to the great theologian al-Ghazzali.