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 alphabet many letters the Proto-Sinaitic alphabet had nor what their alphabetic order was. Among its descendants, the Ugaritic alphabet had 27 consonants, the South Arabian alphabets had 29, and the Phoenician alphabet 22. These scripts were arranged in two orders, an "ABGDE" order in Phoenician and an "HMĦLQ" order in the south; Ugaritic preserved both orders. Both sequences proved remarkably stable among the descendants of these scripts. The letter names proved stable among the many descendants of Phoenician, including Samaritan, Aramaic, Syriac, Arabic, Hebrew, and Greek alphabet. However, they were largely abandoned in Tifinagh, Latin and Cyrillic. The letter sequence continued