Ounce - Wikipedia

The ounce (abbreviated oz; apothecary symbol: ℥) is a unit of mass, weight, or volume used in most British derived customary systems of measurement.

ounce - Wiktionary

A British imperial fluid ounce, with a volume of 1/20 of an imperial pint, 1.733871 cubic inches or 28.413063 millilitres. A little bit. He didn't feel even an ounce of ...