Sestertius

The sestertius (pl.: sestertii) or sesterce (pl.: sesterces) was an ancient Roman coin. During the Roman Republic it was a small, silver coin issued only on rare occasions. During the Roman Empire it was a large brass coin.

The name sestertius means "two and one half", referring to its nominal value of two and a half asses (a bronze Roman coin, singular as), a value that was useful for commerce because it was one quarter of a denarius, a coin worth ten asses. The name is derived from semis, "half" and tertius, "third", in which "third" refers to the third as: the sestertius was worth two full asses and half of a third.

English-language sources routinely use the original Latin form sestertius, plural sestertii; but older literature frequently uses sesterce, plural sesterces, terce being the English equivalent of tertius. A modern shorthand for values in sestertii is IIS (Unicode 𐆘), in which the Roman numeral II is followed by S for semis, and the whole struck through; but because this symbol and striking through letters are not always convenient, HS may be used instead, with the horizontal bar of the 'H' representing the strike through the numeral II, rather than the letter H.

History

The sestertius was introduced c. 211 BC as a small silver coin valued at one-quarter of a denarius (and thus one hundredth of an aureus). A silver denarius was supposed to weigh about 4.5 grams, valued at ten asses, with the silver sestertius valued at two and a half asses (1.125 grams). In practice, the coins were usually underweight.

When the denarius was retariffed to sixteen asses (due to the gradual reduction in the size of bronze denominations), the sestertius was accordingly revalued to four asses, still equal to one quarter of a denarius.