Opinions differ on the origin of his second name, "Tosefa'ah", seemingly from the Aramaic word tosefta (addition).
[1] Others say he was an expert in the braitot and Tosefta which supplement the main works of the Oral Torah.
[5] He succeeded Mar bar Rav Ashi as head of the Sura Academy, a position he held for six years (approximately 467-474).
[9] His chief work was to complete, by additions and amplifications, the compilation of the Talmud begun by Rav Ashi.
These additions consisted for the most part of short, explanatory remarks, indispensable for an understanding of Talmudic themes or for deciding between the conflicting opinions of older authorities.