Explanation of Ancient Roman Technical Terms by Kenneth Wellesley

Auxiliaries cavalry regiments and infantry cohorts (battalions), each about 500 or l,000 men strong, raised from non-Roman provincials and commanded by prefects, Roman officers who had served in the legions. These units were more mobile than the legions, to which they gave support on the flanks, front and rear. Their total strength throughout the territory of the empire was some 180,000 men.
Capitoleither the Capitoline Hill, with or without the adjacent Arx (see map) or the principal building on it, the Temple of Jupiter Best and Greatest.
Centurion commander of a legionary half-company (century) of some eighty men. The centuries were paired to form a full company (maniple), one centurion being senior to the other.
Client a dependant such as a freedman (or his descendant), who remained after emancipation under a legal and moral obligation to render services to his ex-master (patron) in return for favours and protection. Rulers of small kingdoms on the fringe of the empire, client-kings, stood in a similar relationship to the emperor, and could rely on Roman support so long as they retained the confidence of the suzerain.
Consul the highest executive official or 'magistrate' of the Roman People, and president of the senate. At any one time, there were two consuls acting as colleagues. Elected by the senate and with the emperor's approval for terms of two, four or six months, they were called suffect if entering office after the initial pair of each year, after whom it was named. After election and before the assumption of the consulship, a consul-elect was called designate. A repeated, and particularly a third, tenure was a proof of high status and imperial favour. An ex-consul (consular) was competent to hold the most senior commands abroad.
Freedman an ex-slave who had bought or been given his emancipation or 'manumission'; see client. The 'freedmen of Caesar' formed a class of senior civil servants wielding considerable power as members of the emperor's secretariat.
Imperial Agent a financial officer (knight or freedman) administering the imperial domain in a province, subordinate in rank and status to the governor but responsible directly to the emperor.
Knight a member of the equestrian order, a class of Romans determined by birth and financial position, and inferior to the senatorial order. No obligation lay upon knights to serve the state, but if they chose an official career, a wide range of the less important executive and military positions lay open to them.
Legion a heavy infantry formation numbering some 5,000 men who were Roman citizens recruited from Italy and the more-highly Romanized provinces. It was officered by a commander (legate), normally of the rank of praetor, by six staff-officers (tribunes), and by sixty company commanders (centurions). The men were equipped with spear, sword, dagger, helmet, body-armour and semi-cylindrical shield, and were used as a heavy thrusting force designed to cut a way through any opposition. When not actively campaigning, the legion was regularly employed on fortification, road-building and other ancillary tasks. It possessed a cavalry and artillery element. At the time with which the Histories are concerned there were some thirty legions with a total strength of about 150,000 men.
Magistrate an official elected by the senate for a yearly term (in the case of consuls, for less than a yearly term) to conduct the deliberative, judicial and executive functions of the Roman People. The main grades, in ascending order of seniority, are: Quaestor, Praetor, Consul. After serving in Rome, they could expect promotion to posts of appropriate seniority abroad.
Palace a complex of buildings of many kinds occupying most of the Palatine Hill south west of the forum, and including the residence of the emperor.
Praetor one of eighteen annual magistrates with judicial functions. The minimum age of tenure was normally thirty years.
Pretorian Guard a corps d'elite, mostly serving in a ceremonial capacity in Rome and in immediate attendance on the emperor. There were nine (under Vitellius sixteen) cohorts of l,000 men each, whose barracks lay outside the walls of Rome on the north east . Each cohort was commanded by a 'tribune', and the whole body by one or more 'prefects', usually of equestrian rank.
Quaestor one of twenty annual 'magistrates' with minor executive and financial functions. The minimum age of tenure was normally twenty-five years, and election to the quaestorship conveyed membership of the senate.
Rostra a high platform or tribunal in the forum from which magistrates addressed the assembled Roman People.
Tribuneeither a legionary staff-officer or a commander of a pretorian, urban or watch cohort or (as tribune of the plebs) an annually elected official who under the republic exercised a check upon the administrative powers of magistrates by virtue of his veto and legal inviolability; under the principate the office was overshadowed by the tribunician power enjoyed by the emperor.
Triumph a ceremonial procession of troops, commander, prisoners and booty through Rome to the Temple of Jupiter Best and Greatest at the conclusion of a successful campaign. Under the emperors, who were themselves the supreme commanders, only the ornaments were awarded to the field commander.
Urban Cohorts gendarmeric units (four in number and with a strength of 1,000 men each under Vitellius) serving mostly in Rome. Each of these was commanded by a tribune, and the whole force by the chief-of-police (city Prefect).
Watch seven cohorts of police and firemen, each l,000 men strong and commanded by a tribune, responsible for the fourteen regions into which the city of Rome was divided. The whole force was headed by an equestrian prefect of the watch.