JONAH, RABBI (ABULWALID MERWAN IBN JANAH, also R. MARINUS) (c. 990-c. 1050), the greatest Hebrew grammarian and lexicographer of the middle ages. He was born before the year 990, in Cordova, studied in Lucena, left his native city in 1012, and, after somewhat protracted wanderings, settled in Saragossa, where he died before 1050. He was a physician, and Ibn Abi Usaibia, in his treatise on Arabian doctors, mentions him as the author of a medical work. But Rabbi Jonah saw the true vocation of his life in the scientific investigation of the Hebrew language and in a rational biblical exegesis based upon sound linguistic knowledge. It is true, he wrote no actual commentary on the Bible, but his philological works exercised the greatest influence on Judaic exegesis. His first work--composed, like all the rest, in Arabic--bears the title _Almustalha_, and forms, as is indicated by the word, a criticism and at the same time a supplement to the two works of Yehuda 'Hayyuj on the verbs with weak-sounding and double-sounding roots. These two tractates, with which 'Hayyuj had laid the foundations of scientific Hebrew grammar, were recognized by Abulwalid as the basis of his own grammatical investigations, and Abraham Ibn Daud, when enumerating the great Spanish Jews in his history, sums up the significance of R. Jonah in the words: "He completed what 'Hayyuj had begun." The principal work of R. Jonah is the _Kitab al Tankih_ ("Book of Exact Investigation"), which consists of two parts, regarded as two distinct books--the _Kitab al-Luma_ ("Book of Many-coloured Flower-beds") and the _Kitab al-usul_ ("Book of Roots"). The former (ed. J. Derenbourg, Paris, 1886) contains the grammar, the latter (ed. Ad. Neubauer, Oxford, 1875) the lexicon of the Hebrew language. Both works are also published in the Hebrew translation of Yehuda Ibn Tibbon (_Sefer Ha-Rikmah_, ed. B. Goldberg, Frankfurt am Main, 1855; _Sefer Ha-Schoraschim_, ed. W. Bacher, Berlin, 1897). The other writings of Rabbi Jonah, so far as extant, have appeared in an edition of the Arabic original accompanied by a French translation (_Opuscules et traités d'Abou'l Walid_, ed. Joseph and Hartwig Derenbourg, Paris 1880). A few fragments and numerous quotations in his principal book form our only knowledge of the _Kitab al-Tashwir_ ("Book of Refutation") a controversial work in four parts, in which Rabbi Jonah successfully repelled the attacks of the opponents of his first treatise. At the head of this opposition stood the famous Samuel Ibn Nagdela (S. Ha-Nagid) a disciple of 'Hayyuj. The grammatical work of Rabbi Jonah extended, moreover, to the domain of rhetoric and biblical hermeneutics, and his lexicon contains many exegetical excursuses. This lexicon is of especial importance by reason of its ample contribution to the comparative philology of the Semitic languages--Hebrew and Arabic, in particular. Abulwalid's works mark the culminating point of Hebrew