Ounce

An ounce (abbreviated oz; apothecary symbol: ℥) is a unit of mass used in some systems of measurement.

Whilst various definitions have been used throughout history, two remain in common use: the avoirdupois ounce equal to approximately 28.3 g and the troy ounce of about 31.1 g. The avoirdupois ounce is widely used as part of the United States customary and British imperial systems, but the troy ounce is now only commonly used for the mass of precious metals such as gold.