An addendum to Webster 1913: When uncapitalized, the leader of daily prayers in any Muslim community. Not a priest or minister, since Islam has no ordained clergy. When capitalized, a direct blood-line descendant of The Prophet, through Ali, who is entitled by his blood to serve as the leader of all of the Islamic world. The capitalized sort of Imam is recognized only by shi'i Muslims, and never sunnis. The closest sunni equivalent might be a caliph.