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 diacritics or not. Since the Academy of the Hebrew Language ascertains that א in initial position is not transliterated, the symbol for the glottal stop ʾ is omitted from the transliteration, and only the subsequent vowels are transliterated (whether or not their corresponding vowel diacritics appeared in the text being transliterated), resulting in "im", "em" and "om", respectively. The diacritic geresh – "׳" – is used with some other letters as well (ד׳, ח׳, ט׳, ע׳, ר׳, ת׳), but only to transliterate "from" other languages "to" Hebrew – never to spell Hebrew words; therefore they were not included in this