Pronunciation
Sephardic and Yemenite Jews pronounce this word רִבִּי ribbī ; the modern Israeli pronunciation רַבִּי rabi is derived from an 18th century innovation in Ashkenazic prayer books, although this vocalization is also found in some ancient sources. Other variants are rəvī and, in Yiddish, rebbə. The word could be compared to the Syriac word ܪܒܝ rabi.
In ancient Hebrew, rabbi was a proper term of address while speaking to a superior, in the second person, similar to a vocative case. While speaking about a superior, in the third person one could say ha-rav ("the Master") or rabbo ("his Master"). Later, the term evolved into a formal title for members of the Patriarchate. Thus, the title gained an irregular plural form: רַבָּנִים rabbanim ("rabbis"), and not רַבָּי rabbay ("my Masters").
Read more about this topic: Rabbi