Definition: An ounce (symbol: oz) is a unit of mass in the imperial and US customary systems of measurement. There are different types of ounces, but the most common is the avoirdupois ounce, which is equal to approximately 28.35 grams.

History/origin: The ounce has ancient origins and has been used in various forms for centuries. The avoirdupois ounce became standardized in England and was adopted by the US customary system.

Current use: Ounces are used for measuring the mass of food items, precious metals, and other commodities in countries that use the imperial or US customary systems.