CÆSAR, in Roman antiquity, a title borne by all the emperors, from Julius Cæsar to the destruction of the empire. It was also used as a title of distinction for the intended or presumptive heir of the empire, as king of the Romans is now used for that of the German empire.
This title took its rise from the surname of the first emperor, C. Julius Cæsar, which, by a decree of the senate all the succeeding emperors were to bear. Under his successor, the appellation of Augustus being appropriated to the emperors, in compliment to that prince, the title Cæsar was given to the second person in the empire, though still it continued to be given to the first; and hence the difference betwixt Cæsar used simply, and Cæsar with the addition of Imperator Augustus.
The dignity of Cæsar remained to the second of the empire, till Alexius Comnenus having elected Nicephorus Melissenus Cæsar by contract; and it being necessary to confer some higher dignity on his own brother Isaacius, he created him Sebastocrator with the precedence over Melissenus; ordering, that in all acclamations, &c. Isaacius Sebastocrator should be named the second, and Melissenus Cæsar the third.