Abbreviations on Roman Imperial Coins

IMP - IMPERATOR: The title that English adopted to mean 'Emperor' meant 'leader of the army' to the Romans. The award was generally taken on becoming Emperor and renewed whenever a particularly important victory was celebrated. In some cases, these subsequent awards, denoted by a numeral following IMP, allow dating of coins to a very short period. Other Emperors made little use of the title and only assumed the initial award. Our example of Domitian shows IMP XXII; each of the other coins uses the initial IMP without numeral.
CAES, CAE, C - CAESAR: The family name of the first Emperors recalled their being related to Julius Caesar. Even after there was no 'blood' relationship, the term was applied to the Imperial family. When used alone or with an abbreviation for 'Noble' (NC, NOB C, NOB CAES etc), Caesar denoted a junior person, usually a son or the heir apparent.
AVG - AVGVSTVS: Augustus was the title that actually meant 'Emperor'. The first Emperor made the title ('Revered') almost a personal name and it was assumed on ascension by each successive ruler. Until the late Empire, Emperors were both Caesar and Augustus but toward the end the title Caesar was dropped or reserved for the junior members of the imperial family. When there were two emperors, the plural is sometimes shown as AVGG. More rarely (see Numerian below) AVGGG indicated there were three rulers.
PM, PONT MAX - PONTIFEX MAXIMVS: 'Greatest Priest' was held by the most senior ruler when there was more than one Augustus with the others being simply PONTIFEX. The title denoted the position of the Emperor as head of the state religion. PM was not used after the Empire became Christian and the title was (and still is) used by the Pope.
TRP, TRIB POT, P - TRIBVNICIA POTESTAS: An important Republican office was Tribune of the People (plebs) with the power to veto acts of the Senate. The office was first taken on ascension and renewed annually. At first the renewals dated to 10 December (the traditional date) but some rulers used the anniversary of their ascension or 1 January so it is necessary to know which system was in use before dating each reign. Many coins are seen dated with a split year (e.g. 11/12 AD) which means the TRP numeral placed the coin from 10 Dec 11 to 9 Dec 12. From the time of Septimius Severus, 1 January was used regularly. When TRP with numeral is used, it is the best dating device found on Roman coins. TRP with no numeral was the form for the first year; TRP I was not used. Occasionally TRP was used without a numeral even though the coin was struck after the first regnal year. Note the as of Tiberius used to illustrate SC used a long form spelling of TRP. As time went on the shorter abbreviations became standard.
COS, CONS, CO, C - CONSVL: Highest of the offices under the Republic was one of the two annually available consulships. Under the Empire, the office of Consul remained of some importance and was held by the Emperor and his family members with some frequency. Few Romans were ever allowed to serve as Consul more than twice. The exception, of course was the Emperor who could serve whenever the mood struck. As with TRP and IMP the lack of a numeral can mean the first consulship or simply that the numeral was not expressed on the coin. Septimius Severus (Emesa mint) used a few rare variations (IIC, IICO and COS I) and Probus used CONS( below). Commodus and Gallienus have issues with C and a numeral. Otherwise, the standard form is COS + the numeral denoting the number of consulships served (here Domitian has 16 and Trajan 2). The Antoninus Pius here reads COS DES II indicating the Emperor had been designated to serve his second consulship starting on the first day of the new year but that the coin was struck before that date.
PP - PATER PATRIAE: Pater Patriae (Father of his Country) was held by most Augusti but was usually not assumed at the very beginning of the reign. The traditional (and not always observed) practice saw the new Augustus decline the honor of PP and wait a while until he had proven himself worthy of so great a title. Of our sample coins, PP is shown on the Domitian from his twelfth year and not on the Trajan or Antoninus, both first year coins. Strangely, it is shown on the first year Hadrian who did not use the title again for ten years. The premature use of PP was probably an error at the mint which was soon corrected leaving a small number of these 'politically incorrect' coins.
GERM DAC PART etc.: Germanicus, Dacicus, Parthicus and several other similar titles refer to the Emperor being the defeater of the Germans, Dacians, Parthians etc. Use of the titles match the then current operations of the Roman armies.
CENS P, CENS PERP: Censor Perpetuus refers to the Emperor's permanent holding of the old Republican office of Censor. The Censor had the power to rule on who was entitled to be a Roman Senator.
F: Filius (son) follows the name of the father (usually the preceding ruler). There are also coins using N for nepos (grandson) or PRON, pronepos (great grandson).
PF, P FEL, FEL: Various abbreviations for Pius and Felix (pious, happy), used together or separately, became common in the third century.
N, NOST: Noster (our) occasionally modified a title before it became common as part of DN during the fourth century (below).
INV: Invictus (undefeatable) was occasionally used in the late third and early fourth centuries.
XXI, KA: Roman or Greek numerals for 21 specify an alloy of one part silver to 20 parts copper. This was commonly used from the currency reform of Aurelian to that of Diocletian. See my XXI page. At Ticinum, on occasion, alloy was expressed XX (omitting the I) following the workshop letter and preceeding the city initial (on the Probus here: TXXT).
MAX: Maximus (greatest) was used by Constantine I who is now known as 'the Great'. During his life no one would have questioned his right to the superlative.
SM, P: Sacra Moneta (sacred money) or Pecunia (coin) sometime was included in the mintmark.
VOT: Vota (vows) followed by a numeral refers to pledges made by the emperor for faithful service for the period of years. Sometimes the vows of an earlier period were renewed for a longer period resulting in (for example) VOT X ET XX or VOT X MVLT XX.
PERP: Perpetuus (forever) was used in the first century with Censor (above) and more generally in various manners in the later periods.
DN: Dominus Noster (our lord) became a common start for the Imperial titles as the position of Emperor became less the first citizen of the Republic and more the totalitarian despot of the later period.
DV, DIV, DIVO: Divus (divine) was applied to consecrated deceased rulers.
PT: Pater (father) is used with AVGG = 'Father of the Augusti'
VNMR: Venerabilis memoria (revered memory) was used on the consecration coins of Constantine the Great.
The photos on this page show several abbreviations not yet covered by the text and there are many more not shown. Missing from this discussion is coverage of the mintmarks including city abbreviations and the workshop system codes. This will give me something to use for future updates