Greek diacritics - Wikipedia
https://en.wikipedia.org/wiki/Greek_diacriticsGreek orthography has used a variety of diacritics starting in the Hellenistic period. The more complex polytonic orthography (Greek: πολυτονικό σύστημα γραφής, romanized: polytonikó sýstīma grafī́s), which includes five diacritics, notates Ancient Greek phonology. The simpler monotonic orthography (Greek: μονοτονικό σύστημα γραφής, romanized: monotonikó sýstīma grafīs), introduced in 1982, corresponds to Modern Greek phonology, and requires only two diac…