The denarius was the standard silver currency of Rome from around 211 BCE.
Rome introduced the coin during the Second Punic War, probably to help finance military operations against Carthage. It initially contained about 4.5 grams of silver and was valued at ten asses, reflected by the Roman numeral X often shown on early examples.
The denarius remained central to Roman commerce for centuries. Its weight and silver content gradually declined, especially during the later Empire, as emperors altered the coinage to meet financial pressures. The debased antoninianus eventually became more important than the denarius in the third century CE.
The name survived in several later monetary terms. The Arabic dinar and the medieval European denier both ultimately derive from denarius. The denarius should not be confused with the aureus, Rome’s principal gold coin, or the sestertius, a larger accounting and currency unit.