vicarius.

About vicarius

Within the administrative structure of the Roman Empire, an imperial vicar or exarch was a high ranking state official who served as a regional governor, and the office also continued to exist in the early Byzantine Empire. Since the time of emperor Diocletian (284-305), imperial vicars were appointed as civilian governors of newly established imperial dioceses, each of them encompassing several provinces. In the eastern parts of Roman Empire, dominated by the Greek language and common use of Greek terminology, imperial vicars were called exarchs.