strictly the ruler over the fourth part of a province; but the word denotes a ruler of a province generally ( Matthew 14:1 ; Luke 3:1 Luke 3:19 ; 9:7 ; Acts 13:1 ). Herod and Phasael, the sons of Antipater, were the first tetrarchs in Palestine. Herod the tetrarch had the title of king ( Matthew 14:9 ).

These dictionary topics are from
M.G. Easton M.A., D.D., Illustrated Bible Dictionary, Third Edition,
published by Thomas Nelson, 1897. Public Domain, copy freely.