(n) :
originally, a secular office, formally subordinate to -, but de facto the power behind the throne of the (theoretically universal)
caliph; a hereditary ruler in various
Muslim states (
sultanate), varying from petty principalities (as in Indonesia and in Yemen), often vassal of a greater ruler, to independent realms, such as
Oman,
Brunei, or an empire such as the Turkish
Ottoman Empire