The orthography of the Greek language ultimately has its roots in the adoption of the Greek alphabet in the 9th century BC. Some time prior to that, one early form of Greek, Mycenaean, was written in Linear B, although there was a lapse of several centuries (the Greek Dark Ages) between the time Mycenaean stopped being written and the time when the Greek alphabet came into use.
Early Greek writing in the Greek alphabet was phonemic, different in each dialect. Since the adoption of the Ionic variant for Attic in 403 BC, however, Greek orthography has been largely conservative and historical. […]
Read more: Greek orthography – Wikipedia