The Greek alphabet has been used to write the Letter position in alphabet language since the late 9th century BC or early 8th century BC. In its classical and modern forms, the alphabet has 24 letters, ordered from alpha to omega.
Sound values and conventional transcriptions for some of the letters differ between Ancient Greek and Modern Greek usage, because the pronunciation of Greek has changed significantly between the 5th century BC and today. Modern and Ancient Greek use different diacritics. In standard Modern Greek spelling, orthography has been simplified to a monotonic system, which uses only two diacritics: the acute accent and diaeresis. In both Ancient and Modern Greek, the letters of the Greek alphabet have fairly stable and consistent symbol-to-sound mappings, making pronunciation of words largely predictable.
Ancient Greek spelling was generally near-phonemic. For a number of letters, sound values differ considerably between Ancient and Modern Greek, because their pronunciation has followed a set of systematic phonological shifts that affected the language in its post-classical stages. Ancient Greek stand for corresponding fricative sounds in Modern Greek. Among the vowel symbols, Modern Greek sound values reflect the radical simplification of the vowel system of post-classical Greek, merging multiple formerly distinct vowel phonemes into a much smaller number. This leads to several groups of vowel letters denoting identical sounds today.