History of the Greek alphabet retained the sound. A symbol based on the left-hand half ( ├ ) of the letter Η was therefore sometimes used to indicate the presence of where necessary, and its absence was indicated by a symbol based on the right half. During the classical period, ΕΙ came to be pronounced and ΟΥ came to be pronounced , Υ having meanwhile moved to . By about 200 BC, a system of diacritical marks was invented, representing the tone accents in use in Ancient Greek. This also helped to indicate the length of the vowels Α, Ι, and Υ in certain cases
History of the Arabic alphabet History of the Arabic alphabet The history of the Arabic alphabet concerns the origins and the evolution of the Arabic script. It is thought that the Arabic alphabet is a derivative of the Nabataean variation of the Aramaic alphabet, which descended from the Phoenician alphabet, which, among others, gave rise to the Hebrew alphabet and the Greek alphabet (and therefore the Cyrillic and Roman alphabets). The Arabic alphabet evolved either from the Nabataean, or (less widely believed) directly from the Syriac. This table shows changes undergone by the shapes of the letters from the Aramaic original to the Nabataean and