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 letters G, J, U, W, Y, and Z, as well as some other differences. C, K, and Q in the Roman alphabet could all be used to write both the and sounds; the Romans soon modified the letter C to make G, inserted it in seventh place, where Z had been, to maintain the gematria (the numerical sequence of the alphabet). Over the few centuries after Alexander the Great conquered the Eastern Mediterranean and other areas in the third century BCE, the Romans began to borrow Greek words, so they had to adapt their alphabet again in order to write