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) text than serif faces. Without serifs, an uppercase "I" () is indistinguishable from a lowercase "l" (). The average distribution of letters, or the relative frequency of each letter's occurrence in text in a given language, can be obtained by analyzing large amounts of representative text. This information can be useful in cryptography and for other purposes, such as song lyrics. Letter frequencies vary in different types of writing. Letter (alphabet) A letter is a grapheme (written character) in an alphabetic system of writing. It is a visual representation of the smallest unit of spoken sound. Letters broadly correspond to