The Mishnah or Mishna (Hebrew: משנה, "repetition", from the verb shanah שנה, or "to study and review", also "secondary" (derived from the adj. שני)) is the first major written redaction of the Jewish oral traditions called the "Oral Torah" and the first major work of Rabbinic Judaism. It was redacted c. 220 CE by Yehudah Hanasi when the persecution of the Jews and the passage of time raised the possibility that the details of the oral traditions dating from Pharisaic times (536 BCE - 70 CE) would be forgotten. It is thus named for being both the one written authority (codex) secondary (only) to the Tanach as a basis for the passing of judgment, a source and a tool for creating laws, and the first of many books to complement the Bible in a certain aspect.
The Mishnah is also called Shas (an acronym for Shisha Sedarim - the "six orders") », in reference to its six main divisions. Rabbinic commentaries on the Mishnah over the next three centuries were redacted as the Gemara, which, coupled with the Mishnah, comprise the Talmud.