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
Albanian alphabet and Jani Vreto created an alphabet. This was based on the principle of "one sound one letter" (although the revision of 1908 replaced the letter "ρ" by the "rr" digraph to avoid confusion with "p"). This was called the "Istanbul alphabet" (also "Frashëri alphabet"). In 1905 this alphabet was in widespread use in all Albanian territory, North and South, including Catholic, Muslim and Orthodox areas. One year earlier, in 1904 had been published the Albanian dictionary () of Kostandin Kristoforidhi, after the author's death. The dictionary had been drafted 25 years before its publication and was written in the Greek