Denarius

The denarius was the standard silver coin of ancient Rome. First struck around 211 BCE, during the Second Punic War, it remained the backbone of Roman silver coinage for more than four centuries, until heavy debasement in the third century CE pushed it out of production. Its name lived on long after the coin itself, in the silver penny of medieval Europe and in the word dinar.

The name means "containing ten", because the coin was first valued at ten bronze asses. It sat at the centre of a system that eventually ran from the gold aureus down to the brass sestertius and the copper as, and it served as Rome's main medium of exchange for soldiers' pay, taxes and trade.

Before the war with Carthage, Rome produced only limited silver coinage, much of it modelled on the Greek coins of southern Italy. The financial strain of the conflict led to a reorganised system around 211 BCE, a date supported by archaeological finds at Morgantina in Sicily. The new coin weighed about 4.5 grams and showed a helmeted head of Roma on the obverse with the mark X for its value of ten asses, and the twin horsemen known as the Dioscuri on the reverse. Its weight was soon reduced, settling at around 3.9 grams, roughly one eighty-fourth of a Roman pound, by the late second century BCE.

In the 140s BCE the denarius was retariffed at sixteen asses, while keeping its old name. Under Augustus the relationships were fixed: one aureus was worth 25 denarii, and one denarius was worth four sestertii or sixteen asses. The coin was similar in size to the Greek drachma, and in the eastern provinces the two were often treated as roughly equal.

Republican coinage was supervised by a board of three junior magistrates, the tresviri monetales, appointed each year to oversee the striking of bronze, silver and gold. From the second century BCE these moneyers increasingly placed their own names on the coins and chose designs honouring their family's ancestors, legends and past achievements. The result is a remarkably varied series that historians use to trace the politics of leading Roman families. The coins were still issued on the authority of the Roman state, not as private money. In the late Republic, generals such as Julius Caesar also struck coins in their own names, and under Augustus the moneyers' names disappeared from the coinage as minting came under imperial control.

Under the emperors the denarius carried the ruler's portrait and titles, which made it a tool of political messaging as well as money. In 64 CE Nero reduced both its weight and its silver content, and later emperors continued to lower the fineness to stretch limited silver supplies and meet military costs. By the reign of Septimius Severus at the end of the second century, most metallurgical studies put the silver content at roughly half.

In 215 CE Caracalla introduced a larger silver coin, now called the antoninianus, which appears to have been valued at two denarii while containing less silver than two. As Gresham's law would predict, older and better coins tended to be hoarded while the new pieces circulated. Regular issues of the denarius petered out by the middle of the third century, as the antoninianus itself declined into a silver-washed bronze coin during a period of severe currency debasement and inflation.

The denarius survived as a unit of account after it stopped being minted. Diocletian's Edict on Maximum Prices of 301 CE expressed prices in denarii, although by then the unit bore little relation to the old silver coin.

Roman denarii also travelled far beyond the empire. Hoards have been found in Scandinavia, eastern Europe and southern India, where early imperial coins arrived through trade across the Indian Ocean. The name was carried forward by the Carolingian denier and the English penny, which kept the abbreviation "d." in the British pounds, shillings and pence system until decimalisation in 1971. The word dinar, applied to Kushan gold in ancient India and later to the Umayyad dinar of the Islamic world, also derives from denarius, as do the Italian denaro and the Spanish dinero.

In the New Testament the denarius appears as a day's wage for a labourer and as the "tribute penny" shown to Jesus, which helped to fix it in the popular imagination for centuries.

• British Museum: Collection online
• American Numismatic Society