Abū I-Walīd Jonah ibn Janāḥ is undoubtedly one of the greatest Hebrew grammarians. Born in Al-Andalus at the end of the tenth century he was active during the eleventh century, but his exact dates are not known. His best known works, a grammar, Kitāb al-Lumaՙ (The book of variegated flowerbeds) and a dictionary of biblical Hebrew, Kitāb al-'Uṣūl (The book of roots), represented the most important development in the knowledge of Hebrew of the Middle Ages. Other important works on grammar include Kitāb al-Taswi'a (The book of annexation), a short grammatical treatise which he composed as a response to critics of a previous work entitled Kitāb al-Mustalḥaq (The book of annexation).