Av Beit Din,
Av Beis Din, or
Abh Beyth Diyn (abbreviated:
AB"D) (, "Chief of the Court") was the second-highest-ranking member of the
Sanhedrin during the
Second Commonwealth period. The president, who bore the title
Nasi, was in a way the supervisor, but not a member of the court, which consisted of seventy members. The most learned and important of these seventy members was called Av Beit Din, a title similar to that of vice-president.