The transition of the Byzantine Empire to Greek-speaking can be attributed to several factors. Firstly, the Eastern Roman Empire, which eventually became known as the Byzantine Empire, had a significant Greek-speaking population within its territories. Over time, the influence of Greek culture and language became more pronounced, particularly in the eastern regions of the empire.

Additionally, the Byzantine Empire's administrative and intellectual elite gradually shifted from using Latin to using Greek as the primary language of communication and scholarship. This transition was influenced by the prominence of Greek as a language of learning and literature in the eastern Mediterranean region.

Furthermore, the rise of Christianity as the dominant religion in the Byzantine Empire also played a role in the shift to Greek. The New Testament was originally written in Greek, and as Christianity became more influential, the use of Greek as the language of religious texts and liturgy further solidified its position within the empire.