The 'Kitab al-Taswi'a' or 'Book of Reprobation' by Jonah Ibn Janah. A revision of J. and H. Derenbourg's edition

In this article I study several linguistic aspects of the Kitab al-taswi's or Book of Reprobation, a Judaeo-Arabic grammatical treatise written in the eleventh century by the Andalusian grammarian Jonah ibn Janah. I start by analysing the various misinterpretations of the title that have been made, partly due to the erroneous reading on the part of the Derenbourgs in their 1880 edition and translation of the Kitab al-taswi'a. I then compare the t wo complete available manuscripts of this work and give a list of linguisti c features not reflected in the Derenbourgs' edition, but that can be inclu ded among the typical traits of Medieval or Classical Judaeo-Arabic.