Byzantine Greek

Byzantine Greek, also called Medieval Greek, covers the form of the Greek language used across the Byzantine Empire from roughly the fourth or fifth century through the empire's fall to the Ottomans in 1453, developing from Koine Greek while incorporating grammatical simplification and vocabulary change over its roughly thousand-year span, and belonging, like all historical Greek registers, to the Hellenic branch of the Indo-European family. Byzantine Greek functioned as the primary language of the Eastern Roman Empire's imperial administration, its highly educated literary elite, and crucially its Orthodox Christian Church, whose major theological councils, including Chalcedon in 451 and the later iconoclasm controversies of the eighth and ninth centuries, were conducted and their conclusions recorded substantially in this evolving form of Greek.

The Byzantine liturgical and theological tradition, including the Divine Liturgy of St John Chrysostom still used across Eastern Orthodoxy today, and the extensive corpus of Byzantine patristic and monastic writing, including major figures such as Maximus the Confessor and John of Damascus, represent one of Christianity's largest bodies of theological literature in any single historical language register.

Byzantine Greek theological literature produced sustained and highly technical doctrinal debate across the empire's history, including the Christological controversies that split the Byzantine church from the Oriental Orthodox churches following Chalcedon in 451, the iconoclasm controversy over the legitimacy of religious images that convulsed Byzantine religious life through the eighth and ninth centuries before iconodule theology prevailed, and the fourteenth-century Hesychast controversy, in which the monk Gregory Palamas defended contemplative monastic prayer practices and a distinction between God's unknowable essence and knowable energies, a formulation that became authoritative Orthodox theology and remains influential in modern Eastern Orthodox spirituality. Byzantine Greek liturgical texts, hymnody and monastic literature continue to be studied directly by Orthodox seminarians and scholars, and Mount Athos, the autonomous Orthodox monastic community in Greece, maintains manuscript collections and living scholarly engagement with Byzantine Greek theological and liturgical texts largely unbroken since the Byzantine period itself, giving Byzantine Greek a continuous institutional life within Orthodox Christianity distinct from the purely academic study it receives in secular universities.