EMPEROR (see also Caesar). In modern usage an emperor rules an area larger than a single kingdom. In Rom. law and custom two significant ideas are found. First, however dictatorial he may have been, the emperor was thought of as exercising imperium (Lat.: the properly delegated authority to command in behalf of the state). By contrast, kings ruled by virtue of personal legitimacy or personal authority. Second, the emperor was the one declared ruler or imperator by the Rom. armies (this custom clearly contradicts the spirit of the first idea). Most historic European “emperors” traced the legal origins of their title from the Rom. emperors.

None of these distinctions are significant for Biblical usage. Cyrus, Nebuchadnezzar, and Caesar all are referred to as “king” (Ezra 1:1; Dan 3:9, and John 19:15, respectively). Moreover, in contrast to the rich theological connotations of “king” (q.v.) in Scriptures no theological concepts are attached to the office of emperor. Christ as ruler is “King of kings” (Rev 19:16) rather than “Emperor.”

International Standard Bible Encyclopedia (1915)

ho sebastos; Latin augustus:

The title of the Roman emperors; (Ac 25:21,25).

See Augustus; nodetitle.