Tetrarch
Archimandrite Nikifor’s Biblical Encyclopedia
(Luke 3:1)—originally the ruler of one fourth of a territory, but later a more general title for a subordinate regional prince under Roman authority. In the New Testament Herod Antipas, Philip, and Lysanias are called tetrarchs. A tetrarch could colloquially be called a king, though the formal titles were not identical. Herod the Great received the title tetrarch before Rome later recognized him as king of Judea.