Imperium

Imperium is a Latin word which, in a broad sense, translates roughly as 'power to command'. In ancient Rome, different kinds of power or authority were distinguished by different terms. Imperium referred to the ability of an individual to command the military. It is not to be confused with auctoritas or potestas, different and generally inferior types of power in the Roman Republic and Empire. Primarily used to refer to the power that is wielded, in greater or lesser degree, by an individual to whom it is delegated, the term could also be used with a geographical connotation, designating the territorial limits of that imperium. Individuals given such power were referred to as curule magistrates or promagistrates. These included the curule aedile, the praetor, the censor, the consul, the magister equitum, and the dictator.

In ancient Rome, imperium could be used as a term indicating a characteristic of people, the wealth held in items, or the measure of formal power they had. This qualification could be used in a rather loose context (for example, poets used it, not necessarily writing about state officials). However, in Roman society it was also a more formal concept of legal authority. A man with imperium ("imperator") had, in principle, absolute authority to apply the law within the scope of his magistracy or promagistracy. He could be vetoed or overruled either by a magistrate or promagistrate who was a colleague with equal power (e.g. a fellow consul) or by one whose imperium outranked his - that is, one of imperium maius (greater imperium).

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