How did the Eastern Roman Empire become the Byzantine Empire?

The Eastern Roman Empire and the Byzantine Empire were the same political entity; the term "Byzantine" is a historiographical label applied by later scholars to distinguish the medieval state from its ancient Roman predecessor.12

The transition was not a sudden event but a gradual transformation. While the state functioned as the Eastern Roman Empire following the split of the empire in 395 CE and the fall of the West in 476 CE, profound changes occurred over several centuries. By the 7th century, the empire’s society, culture, and institutions had diverged significantly from their ancient Roman roots. This evolution was driven by regional traumas, including warfare, pestilence, social upheaval, and the Arab conquests of the 630s.231

Key factors in this transformation included:
* Cultural Shift: During the reign of Heraclius (610–641 CE), the official language of the empire transitioned from Latin to Greek.4
* Geopolitical Focus: The empire’s administrative and intellectual life centered on Constantinople, the "new Rome" founded by Constantine I in 330 CE.2
* Historical Perspective: Its inhabitants continued to identify as Romaioi (Romans) and viewed their state as the legitimate continuation of the Roman Empire until its final collapse in 1453.2