vilayet
/vɪˈlɑːjɛt
/noun
(In Turkey, and formerly in the Ottoman Empire) a major administrative district or province with its own governor.Mesopotamia, as the three vilayets or provinces of Basra, Baghdad and the predominantly Kurdish Mosul that make up modern day Iraq were then known, had been the easternmost part of the Ottoman Empire for several centuries.
Origin
Turkish, from Arabic wilāya(t) 'government, administrative district'.