Ancient Greek has been pronounced in various ways by those studying Ancient Greek literature in various times and places. This article covers those pronunciations; the modern scholarly reconstruction of its ancient pronunciation is covered in Ancient Greek phonology.
Among speakers of Modern Greek, from the Byzantine Empire to modern Greece, Cyprus, and the Greek diaspora, Greek texts from every period have always been pronounced by using the contemporaneous local Greek pronunciation. That makes it easy to recognize the many words that have remained the same or similar in written form from one period to another. Among Classical scholars, it is often called the Reuchlinian pronunciation, after Johann Reuchlin.
Nevertheless, Greek textbooks for secondary education give a summary description of the reconstructed pronunciation of Ancient Greek. That includes the differentiation between short and long vowels and between the various accents; the pronunciation of the spiritus asper as /h/ and the pronunciation of β, γ and δ as plosives and of diphthongs as such. However, there is often no mention of the ancient aspirate pronunciation of θ, φ and χ, which are different from the modern fricative pronunciation.
The theology faculties and schools related to or belonging to the Eastern Orthodox Church use the Modern Greek pronunciation to follow the tradition of the Byzantine Empire.
The study of Greek in the West expanded considerably during the Renaissance, in particular after the fall of Constantinople in 1453, when many Byzantine Greek scholars came to Western Europe. Greek texts were then universally pronounced with the medieval pronunciation that still survives intact.
From about 1486, various scholars (notably Antonio of Lebrixa, Girolamo Aleandro, and Aldus Manutius) judged that the pronunciation to be inconsistent with the descriptions that were handed down by ancient grammarians, and they suggested alternative pronunciations. This work culminated in Desiderius Erasmus's dialogue De recta Latini Graecique sermonis pronuntiatione (1528). The system that he proposed is called the Erasmian pronunciation.