Judah ben David Hayyuj

Judah ben David Hayyuj (Hebrew: יְהוּדָה בֶּן דָּוִד חַיּוּג׳, romanized: Yəhuḏā ben Dawiḏ Ḥayyuj, Arabic: أبو زكريا يحيى بن داؤد حيوج, romanized: Abū Zakariyya Yahyá ibn Dawūd Ḥayyūj) was a Maghrebi Jew of Al-Andalus born in North Africa.

Preceding scholars had found the greatest difficulty in accounting, by the laws of Hebrew morphology, for the divergences existing between the so-called "strong" and "weak" verbs.

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."

This work, probably written before his two chief treatises, attempts to set forth the features underlying the Masoretic use of the vowels and tone.

A fourth work, the Kitab al-Natf "The Book of Extracts," is known to have been written by Hayyuj, but only a fragment, unpublished as of the beginning of the 20th century, and a few quotations by later authors have survived.