Aelius Donatus, Roman grammarian and rhetorician, taught in Rome AD c.360, and who numbered St. Jerome among his pupils. He is best known as the author of Ars Grammatica (The Art of Grammar). This book was deemed so perfect and was so widely used in the Middle Ages that its author's name, in the form Donat, became synonymous with "grammar text", and indeed the "Donat" was the only standard textbook used in mediaeval education. Latin grammar was reduced to an abridgment of Donatus, supplemented by the meager commentaries of the teacher, and replaced only in the thirteenth century by the "Doctrinale" of Alexander de Villedieu (de Villa Dei). With the exception of some fragments preserved in Servius, the "Life of Virgil" is all that survives of Donatus' commentary on the poems of Virgil.