Evolution of Imperial Rome. . Because the Roman Empire lasted such a long time, historians use various names to distinguish different periods or eras. Such names include Western Roman Empire, Eastern Roman Empire and Byzantine Empire, which are used throughout this article to refer to the Roman Empire or the Western or Eastern part thereof.. . Traditionally, historians make a distinction between the Principate, the period following Augustus until the Crisis of the Third Century, and the Dominate, the period from Diocletian until the end of the Empire in the West. According to this distinction, during the Principate (from the Latin word princeps, meaning "first citizen") the realities of absolutism were formally concealed behind Republican forms; while during the Dominate (from the word dominus, meaning "lord") imperial power was clearly shown, with golden crowns and ornate imperial ritual. More recently historians have established that the situation was far more nuanced: certain historical forms continued until the Byzantine period, more than one thousand years after they were created, and displays of imperial majesty were common from the earliest days of the Empire.. . The extent of the Roman Republic and Roman Empire. . ██ 133 BC. . ██ 44 BC (late Republic, after conquests by republican generals). . ██ AD 14 (death of Augustus). . ██ 117 (maximum extension). . First emperor. The question about who was the first emperor has never found a definitive answer. Under a purely technical point of view there is no clear first emperor, as the title itself was not an official post in the Roman constitutional system - rather, it was an amalgam of separate roles.. . Julius Caesar was a Dictator Perpetuus ("life-long dictator"), which was a highly irregular form of dictator, an official position in the Roman republic. According to law, the rule of a dictator would normally never exceed 6 months. The form created by Caesar was therefore quite contrary to the basic principles of the Roman Republic. Nevertheless, officially his authority rested upon this republican title, however irregular it might have been, and therefore he is considered a republican official. At the very least he pretended to be one. Several senators, among them many former enemies who had been "graciously" pardoned by him, grew fearful that he would crown himself and try to establish a monarchy. Accordingly, they conspired to assassinate him, and on the Ides of March, on the 15 March 44 BC, the life-long dictator perished under the blades of his assassins before he could be crowned.. . Octavian, his grand-nephew, adopted son and political heir, is widely accepted as the first emperor. He had learned from the mistake of his predecessor and never claimed the widely feared title dictator, disguising his power under republican forms much more carefully. All this was intended to foster the illusion of a restoration of the Republic. He received several titles like Augustus - the honorable one, and Princeps - translated as first citizen of the Roman republic or as first leader of the Roman Senate. The latter had been a title awarded for those who had served the state well; Pompey had held that title.. . In addition, Augustus (as he is named thereafter) was granted the right to wear the Civic Crown of laurel and oak. However, it must be noted that officially, none of these titles or the Civic Crown, granted Augustus any additional powers or authority; officially he was simply a highly-honored Roman citizen, holding the consulship. Augustus also became Pontifex Maximus after the death of Marcus Aemilius Lepidus in 13 BC. He also received several additional and extraordinary powers without claiming too many titles. In the end he only needed the authority itself, not necessarily all the respective titles.. . From the Republic to the Principate (31 BC–AD 14). Further information: Praetorian Guard, Roman triumph, Battle