Mishnah (Hebrew, teaching) is Jewish oral law and in particular a collection of oral law completed by Judah ha-Nasi. Originally all oral law was designated as «mishnah» and it was accepted that the mishnah of one tanna was different from that of another.
After Judah ah-Nasi reacted and arranged his six orders of mishnah around the beginning of the sixth century AD it was initially described as «Our Mishnah.» The Mishnah is divided into six sedarim, orders, Zeraim (Seeds), Mo’ed (Festivals), Nashim (Women), Nezikim (Damages), Kodashim (Holy Things), and Tohorot (Purities): the Talmuds are based on these sedarim. Judah ha-Nasi embodied in his collection many earlier collections: he «systematized the mishnayot; they had been previously systematized, but he stated the halakhah both anonymously and and according to the views of a score of disciples of the sages…
Thus the final text contains many different styles as well as an enormous variety of opinion.» (Samsom and Chinon) At the same time Judah ha-Nasi laid down his personal rulings which is why the amoraim on occasion assert, «the Mishnah represents an individual opinion,» (B.Suk.19b) Because of such combining and selecting of existing collections, Judah ha Nasi’s Mishnah became representative of the entire community and authoritative, although other collections were attempted, such as Tosefta.
Later commentators debate as to whether early mishnah collections were in writing, and it is argued that Judah ha-Nasi’s Mishnah was only taught orally. Different sequences of the six sedarim are given by Resh Lakish and R. Tanhuma which argues for an oral transmission. Each seder is divided into massekhtot, treaties.
The sequence of the treaties differs within the orders of the different manuscripts. The text was also emended by later teachers; the most important early manuscripts are the Kaufman manuscript in Budapest, the Parma manuscript, the Oxford manuscript which contains the Maimonides’ commentaries, and the Cambridge manuscript. It was first printed in Spain in 1485, but the first complete surviving edition was printed in Naples in 1492. A.G.H.
Bowker, John, The Oxford Dictionary of World Religions, New York, Oxford University Press, 1997, pp. 645-646