the ruler of a Muslim country (especially of the former Ottoman Empire)
"The historical documentary focused heavily on the sultan's struggle to modernize his empire before it fell in 1922."
The holder of a secular office, formally subordinate to, but de facto the power behind the throne of, the caliph.
"The sultan maneuvered skillfully behind the scenes to ensure his preferred candidate was named as the new caliph without ever appearing at the public ceremony himself."
A surname.
"After graduating from law school, she decided to start her own firm under the name Elena Sultan."