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
Greek alphabet and acute can be "represented" as U+03B1 U+0304 U+0301, this rarely renders well: . There are two main blocks of Greek characters in Unicode. The first is "Greek and Coptic" (U+0370 to U+03FF). This block is based on ISO 8859-7 and is sufficient to write Modern Greek. There are also some archaic letters and Greek-based technical symbols. This block also supports the Coptic alphabet. Formerly, most Coptic letters shared codepoints with similar-looking Greek letters; but in many scholarly works, both scripts occur, with quite different letter shapes, so as of Unicode 4.1, Coptic and Greek were disunified. Those Coptic letters