Praetor was a title granted by the government of Ancient Rome to men acting in one of two official capacities: the commander of an army (in the field or, less often, before the army had been mustered); or, an elected magistratus (magistrate), assigned various duties (which varied at different periods in Rome's history). The functions of the magistracy, the praetura (praetorship), are described by the adjective: the praetoria potestas (praetorian power), the praetorium imperium (praetorian authority), and the praetorium ius (praetorian law), the legal precedents established by the praetores (praetors). Praetorium, as a substantive, denoted the location from which the praetor exercised his authority, either the headquarters of his castra, the courthouse (tribunal) of his judiciary, or the city hall of his provincial governorship.