Originally Posted by davidmich
My question is why still refer to a Roman empire (eg.Byzantine) after its collapse?
Because as the name implies the Western Roman Empire was just the western half of the empire and the Eastern Roman Empire continued to chug right along. The ERE had been the senior ( and wealthier ) half since 330 when Constantine I moved the capital from Ravenna to Constantinople. The term "Roman" had long since ceased to refer exclusively to citizens of the city of Rome - the inhabitants of the ERE/Byzantine empire considered themselves Romans, called themselves Romans and were called Romans by all of their neighbors. Hence historical geopolitical terms like Romania
Historians use the term Byzantine as a useful placeholder for the increasingly Greco-centric post-WRE ERE state to avoid confusion. But it was not contemporary word, only appearing in the Renaissance after the state was defunct. When the Byzantine state existed it was the Roman Empire to just about everyone.