\begin{definition}[Definition:Roman Weights and Measures/Mass/Uncia]
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.
\end{definition}