Judah ben David Hayyuj

Judah ben David Hayyuj (Arabic: أبو زكريا يحيى بن داؤد حيوج Abu Zakariyya Yahya ibn Dawūd Hayyūj) was a Moroccan Jewish linguist. He is regarded as the father of scientific grammar of Hebrew language. He was born in Fez, Morocco, about 945. At an early age he went to Cordoba, where he seems to have remained till his death, which occurred about 1000 CE.

Hayyuj was a pupil of Menahem ben Saruq, whom he later helped to defend against the attacks of Dunash ben Labrat and his followers. Later in life Hayyuj developed his own theories about Hebrew grammar, and was himself obliged to step forward as an opponent of the grammatical theories of his teacher. His thorough knowledge of Arabic grammatical literature led him to apply to the Hebrew grammar the theories elaborated by Arabic grammarians, and thus to become the founder of the scientific study of that discipline. The preceding scholars had found the greatest difficulty in accounting, by the laws of Hebrew morphology, for the divergences existing between the regular, or so-called "strong," verbs and the "weak" verbs. A hopeless confusion appeared to reign here in Hebrew; and much ingenuity was spent in endeavoring to discover the principles that controlled the conjugation of the verbs. The weakness of Menahem's assertion that there are stems in Hebrew containing three letters, two letters, and one letter respectively was pointed out by Dunash; but, although the latter was on the road to a solution of the problem, it was left to Ḥayyuj to find the key.

Hayyuj announced that all Hebrew stems consist of three letters, and maintained that when one of those letters was a "vowel letter," such a letter could be regarded as "concealed" in diverse ways in the various verbal forms. To substantiate his theory he wrote the treatise upon which his reputation chiefly rests, the Kitab al-Af'al Dhawat Huruf al-Lin (The Book of Verbs Containing Weak Letters). The treatise is in three parts: the first is devoted to verbs whose first radical is a weak letter; the second to verbs whose second radical is weak; and the third to verbs whose third radical is weak. Within each division he furnishes what he considers a complete list of the verbs belonging to the class in question, enumerates various forms of the verb, and, when necessary, adds brief comments and explanations. Preceding each division the principles underlying the formation of the stems belonging to the division are systematically set forth in a series of introductory chapters.

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