The Roman Republic may have started around 700 B.C. but the Empire didn’t officially start until Augustus in 27 B.C. and then you have to consider the Eastern Roman Empire which didn’t die until 1453 A.D.
IMO that’s too technical. I think the empire started when they took over all of Italy, Gaul and North Africa, maybe after the Punic Wars.
Wasn’t Julius claiming the title of Imperator and didn’t they already expand into Egypt. I would associate the word with the fact that Roma controlled an empire.
My education continues to grow ... thanks.