Definition:Troy/Ounce

Definition
The troy ounce is a troy unit of mass.
 * $1$ troy ounce $= \dfrac 1 {12}$ troy pound $= 20$ pennyweight $= 480$ grains $\approx 31 \cdotp 1$ grams.

It weighs approximately $\approx 1 \cdotp 1$ ounces avoirdupois.

It is seen that a troy ounce and an apothecaries' ounce have the same mass.