Like all other nations, all provinces in the Roman Empire are not equal. Those that were deemed more important were ruled by 'legates,' while the less important ones by 'prefects' (later 'procurator'). Both were appointed directly by the Emperor; whereas legates usually come from the nobility classes, prefects usually belong to the equestrian order.
Before the time of Caligula (r.37-41) the rulers of minor provinces were termed 'prefects.' The term 'procurator'—with all its military connotations—came into fashion after that.
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