Definition:Roman Weights and Measures/Mass/Uncia

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The uncia is a unit of mass that was part of the Roman system of weights.

$1$ uncia $= \dfrac 1 {12}$ libra $= 24$ scrupuli.

Its value in modern units is estimated to be approximately $423$ grains or $27.4$ grams.

Also see

Historical Note

The uncia continued to be used as a unit of mass in Europe after the fall of Rome, evolving into the ounce.

It is understood to be of the same mass as the apothecaries' ounce and troy ounce, and is about $10 \%$ heavier than the ounce avoirdupois.

Linguistic Note

The word uncia literally means twelfth part, that is: $\dfrac 1 {12}$.

The name derives from the fact that an uncia was $\dfrac 1 {12}$ of a libra.

The plural is unciae.