I am not Jewish I am a Christian but I have a question best asked of someone of the Jewish faith. In ancient times (I am talking about before and after the life of Jesus) I understand teachers were called rabbis. I am not sure if Jesus was called a rabbi during his life or if that was added after his death. However, my question is what criteria or understanding would the people of the time have used to call anyone a rabbi or teacher? Surely there were those who were recognized with more authority than others.
In ancient times, the title “rabbi” was bestowed on somebody by means of ordination, or semichah. Unlike the modern-day concept, this ordination was not given by official bodies, or by the passing of tests, but could be given only by somebody who himself had been granted ordination. According to tradition, this “ordination chain” began with Moses’ ‘ordination’ of Joshua, and continued until the chain was broken, probably around the end of the Talmudic era (around 5 CE; some suggest that it continued into the Gaonic era).
Those who were ordained as “rabbis” had the authority to sit in judgment on a court of law, and were also consulted to decide questions in matters of Torah law. This last function continues in the modern-day rabbi, although he lacks the formal semicha (ordination) that was given in ancient times.
Among those who possessed semicha, there remained a certain hierachy, which was determined both by formal position (the nasi (prince), for instance, was a position of leadership), and by wisdom.
Sources: See Sanhedrin 14; which describes how the Romans wished to abolish the institution of semicha (ordination), knowing its importance to the upkeep of Jewish law.