About the Mystery of the Letters the mid-6th century, in which Mar Saba had played an important role. The anonymous author of the treatise declares he was prompted to the study of the secret meanings of the letters by the words of the Apocalypse, "I am the Alpha and Omega", and that he subsequently received a vision about them on Mount Sinai. The author proposes a re-modelled Greek alphabet reduced to 22 letters on the model of the 22 letters of Hebrew (discounting Xi Ξ and Psi Ψ), and with the Hebrew letter names. He then interprets these letters as symbolic figures of 22 works of
Hebrew alphabet for refining and maintaining the system. These points are normally used only for special purposes, such as Biblical books intended for study, in poetry or when teaching the language to children. The Tiberian system also includes a set of cantillation marks, called "trope", used to indicate how scriptural passages should be chanted in synagogue recitations of scripture (although these marks do not appear in the scrolls). In everyday writing of modern Hebrew, "niqqud" are absent; however, patterns of how words are derived from Hebrew roots (called "shorashim" or "triliterals") allow Hebrew speakers to determine the vowel-structure of a given word