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 Greek alphabet Often, in medieval manuscripts, old uncial letter forms were mixed in with the normal minuscule letters for writing titles or for emphasizing the initial letter of a word or sentence. Like in Latin, this became the root of the modern innovation of letter case, the systematic distinction between uppercase and lowercase letters in orthography. The uppercase letters of modern orthography are derived from the uncial script, while the lowercase letters are derived from minuscules. The invention of printing saw the codification of a more fixed set of letter structures. Greek handwriting made extensive use of ligatures with letters written differently