caliph
The supreme religious and political authority of Muslims, considered successor of Muhammad (Arabic: khalifa = deputy). He was the head of the Caliphate, the religious state of the Arabs.

monostrategos
A term used in Byzantine sources to denote a theme's general when the latter, apart from leading his own troops, also took command of neighbouring themes, either to better organise defence in a broad front or to conduct offensive operations under a unified command.

strategos ("general")
During the Roman period his duties were mainly political. Οffice of the Byzantine state´s provincial administration. At first the title was given to the military and political administrator of the themes, namely of the big geographic and administrative unities of the Byzantine empire. Gradually the title lost its power and, already in the 11th century, strategoi were turned to simple commanders of military units, responsible for the defence of a region.

theme
A Byzantine term that signifies wide military and administrative units under the administration of a strategos (general). The institution was consolidated in the 7th century and was characteristic for the organization and the division of Byzantine Empire at the Middle Byzantine period. The term applies also to the army unit that resided in each administrative unit and was staffed by farmer-soldiers. The thematic system was maintained until the end of Byzantine period. However, in the Later Byzantine period it was used in order to declare mostly tax units.