This volume presents a comprehensive study of Arabic morpho-phonology with its basics and intricacies, by making available a wide range of material from the 8th century A.D. until our days and exploring the main topics that arise. It uses as its point of departure an unused source: the end of the 13th century Marāḥ al-arwāh by Aḥmad b. ‘alī Mas‘ūd, which is critically edited and provided with an introduction, an English translation and an extensive commentary. It offers an analysis of many grammatical theories, paradigms, qur'anical citations, verses of poetry, dialectal variants and Semitic words and concludes with various indices that make the enormous body of information easily accessible.