What key aspects of Rome present it as a clear example of an empire?? (Detailed)

The legacy of the Roman Empire has been varied and impactful, comparable to that of other hegemonic polities of world history (e.g. Persian Empire, ancient Egypt or imperial China).

The Roman Empire itself, built upon the legacy of other cultures such as Ancient Greece, has had long-lasting influence with broad geographical reach on a great range of cultural aspects, including state institutions, law, cultural values, religious beliefs, technological advances, engineering and language.