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
Letter (alphabet) from cultures that use logograms–word symbols–to represent words take years longer to learn to read and write than children learning an alphabet. The relative ease of memorizing twenty-six letters contributed to the spread of literacy throughout the world. The first consonantal alphabet found emerged around 1800 BCE to represent the language of the Phoenicians, Semitic workers in Egypt (see Middle Bronze Age alphabets), and was derived from the alphabetic principles of the Egyptian hieroglyphs. Our present Roman system derives from this Phoenician alphabet, which had twenty-two letters. Nineteen of our present letters evolved from the early Phoenician forms; letter shapes