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 added in the Arabic alphabet include these (except for , which survives as a separate phoneme in Ge'ez ሠ): One modern national alphabet that has not been graphically traced back to the Canaanite alphabet is the Maldivian script, which is unique in that, although it is clearly modeled after Arabic and perhaps other existing alphabets, it derives its letter forms from numerals. Another is the Korean Hangul, which was created independently in 1443. The Osmanya alphabet was devised for Somali in the 1920s by Osman Yusuf Kenadid, and the forms of its consonants appear to be complete innovations. Among alphabets