The best place to find full information on Roman institutions is the Oxford Classical Dictionary (4th edition, 2012). This glossary is designed to help explain terms used in the text.
Adventus The ceremonial entrance of an emperor into a city. The emperor would be welcomed by crowds and speeches, and might hand out gifts to the people. The theme is common on Roman imperial coinages and the ceremony became especially important in the late empire.
ager publicus Land owned by the state, mostly acquired by conquest and leased out to citizens in return for rents (vectigalia).
censor During the Republican period a pair of censors were elected for eighteen months every five years from among the most senior senators. Their duties included reviewing the membership of the senate and equestrian orders, assigning all citizens to their correct political orders and issuing contracts for public works. They also came to exercise moral authority. Under the principate a few emperors took the power of censors or held censorships, and in practice assumed many of their functions.
census Originally the head-count of citizens conducted every year by the censors who also assigned each citizen into an order based on the amount of property he owned. The term later came to be used for periodic assessments of tax-liability in the provinces.
centurions The main officers of the legions whose expertise was vital given the aristocratic commanders were often relatively inexperienced. Most centurions commanded units of 80-100 men, and during the Republic were selected from the most experienced soldiers. Under the principate an elaborate hierarchy of ranks and pay developed, and senior centurions were often detached to act as administrators of various kinds.
consul From the early Republic two consuls were elected every year and jointly acted as chief magistrates of the Roman state. Their duties included convening the senate, presiding at major rituals, leading armies and holding elections.
curiales Members of the councils of provincial cities in the Roman empire. The Greek equivalent term was bouleutai. These groups were in effect local equivalents of the senatorial order in Rome and like them were recruited from the propertied classes.
dictator During times of military emergencies a single dictator was elected in place of the consuls for a limited period only. The term was later appropriated first by Sulla and then Julius Caesar to provide a traditional name for their control of the state.
equites The richest citizens of the Republic were enrolled in the equestrian order from which senators were elected. Equites are also sometimes termed knights, and at times the term equestrian is used to designate any citizen with the requisite property qualification, whether or not they had been formally enrolled as equites equo publico. Augustus created a new senatorial order above the equestrian one, for which the property qualification was higher, and gave both orders specific roles in the government of the empire and the ceremonial of the city.
fasces The attendants of consuls and dictators carried before them an axe bound together into a bundle of rods as a simple of power.
hoplite A Greek term for a heavy-armed infantryman who fought hand to hand in a close formation termed a phalanx.
imperium The term originally meant a command, both one issued and one given to a general. Holding imperium conferred a range of religious and political powers and obligations, and so it was formally assumed at the start of a campaign and laid down at the end of one. The term was extended to mean the authority of the Roman people, and at the end of the Republic came to be used in the term of the territory subject to the commands of the Romans, from which our sense of territorial empire derives.
legate A legate meant a Roman assigned a particular task by the state. Some legates were effectively ambassadors sent to conduct negotiations, some (legati legionis) were commanders assigned to legions, and from the last century BC there were also legates assigned to govern parts of very large provinces, such as that awarded to the emperor.
legion From the middle Republic until the late empire, the Roman army was based on units of around 5,000 heavily armed infantrymen, each of which was termed a legion. Typically these units were supported by light infantry, missile troops, cavalry, engineers and other auxiliaries.
magister officiorum Senior official in the bureaucracy of the late empire and the Ostrogothic kingdom of Italy.
magistrate An official of the Roman state elected by the whole community. The most important magistrates were (in descending order) censors, consuls, praetors and aediles. A dictator or an interrex (a person appointed solely to hold elections) were magistrates, but tribunes (elected only by the plebeians) were not.
patricians This inner circle of families within the equestrian order claimed descent from the aristrocracy of the Regal Period. During the Republic they gradually lost control of a monopoly of magistracies but even under the principate some priesthoods were reserved for patricians. The emperors occasionally created new patricians, as an honour and to provide sufficient for the various patrician priesthoods.
plebeians All members of the Roman state who were not patricians. Tradition recorded a number of conflicts between patricians and plebeians during the early Republic (known collectively as the Struggle of the Orders) through which the prerogatives of the patricians were reduced and the rights of the plebeians recognised, for example in the institution of the tribunate or in the convention that votes of the plebeians (plebiscita) were binding on the entire state.
pontifex maximus The most senior priest of the college of pontiffs, and holder of the most prestigious priesthood in Rome. As well as presiding over the pontiffs he also supervised a number of other priests including the priestesses of Vesta.
populares During the last century of the Republic a series of senatorial politicians, of whom the most famous were the Gracchi brothers and Julius Caesar, based their political programme on fighting for the interest of the Roman people. Land-distributions, colonial schemes, and subsidized or free grain were distinctive features of their activities but in practice they became involved in all political debates, often using popular assemblies to outflank their opponents (who adopted the name Optimates). This conflict contributed to the civil strife of the late Republic.
praetor A magistrate of the Roman state. After the creation of the consulship the praetors were the more junior magistrates and had a range of judicial, administrative and military responsibilities. The number of praetors and the diversity of their roles increased as the city and empire expanded.
praetorian prefect The main bodyguard of the emperors were the praetorian cohorts and their commanders were equestrian prefects. From as early as the reign of Tiberius they came not only to control security in the City (and around the emperor when he was away from it) but also to act as the chief equestrian advisors to the emperor, and effectively as viziers or chief ministers of the imperial court. From the early fourth century AD the empire was divided in praetorian prefectures within which each prefect headed the imperial bureaucracy.
princeps Literally the first (most senior) senator, the title was adopted by Augustus and his successors as a more neutral alternative to rex (king), dictator or perpetual consul.
promagistrate Originally Roman armies were commanded by consuls and praetors but after imperial expansion made this impractical, the senate began to ask former magistrates to take on commands. By the late Republic magistracies seem often to have been regarded as a necessary preliminary to winning a major command, and consuls drew lots for the commands prepared for them. Under the principate the most senior governors (for example of Africa, Asia and Achaea) were Proconsuls, and less senior posts went to propraetors, the emperors reserving for themselves one vast province which they governed through legates (legati Augusti pro praetore).
provincia Originally the task assigned along with imperium to a magistrate or pro-magistrate (e.g. the war with Antiochus, the command of Sicily), the term eventually acquired the sense of a territorial unit within the empire, hence the modern term “province”.
publicanus A Roman citizen who had contracted with the state to carry out work, for example provisioning an army, building or repairing a temple or basilica or road, or collecting taxes. The most notorious publicans were the tax-farmers, whose brutality and greed in the later Republic became proverbial.
senate The council of the Roman state, composed mostly of ex-magistrates but topped up every five-years by the censors from those with the appropriate census qualification.
spolia opima An exceptional honour granted to generals who had killed their counterparts in single combat. Augustus claimed they had to fight under their own auspices to qualify.
tetrarchy In the aftermath of the military crisis of the third century AD, the empire was for a while ruled by colleges of emperors, originally comprising a pair of senior emperors (termed Augusti) and a pair of junior ones (Caesares) who were also their designated heirs. The term “tetrarchy” refers both to this short-lived institution and to the period, while “tetrach” refers to one member of the college. Both joint rule and the distinction between Augusti and Caesares had earlier precedents, but before Diocletian power was always shared between relatives rather than political allies. That was the case once again by the late fourth century AD.
tribune of the People (tribunus plebis) An annually elected position created during the Republic to protect the rights of the plebeians against the patricians. Tribunes’ persons were sacrosanct and they had the right to call assemblies and to veto legislation and the acts of magistrates if they thought them against the interests of the plebeians. During the last century of the Republic the post was used first by the Gracchi and other popularis politicians as a means of passing legislation the senate might not agree to and later by generals in order to have a veto to protect their interests. The emperors appropriated the sacrosanctity of tribunes as one of their powers, and dated their regnal year by the number of annual grants of tribunical power they had received.
triumph This ritual which included a great procession into the city might be awarded to a general who had won a significant victory. The procession was often accompanied by games, banqueting, and extended public holidays. Under the principate only emperors and their relatives celebrated triumphs.