what does OZ Mean

Question

 For example in a sentence :

A;How heavy is this glass of water ?

B;Answers called out ranged from 8 oz. to 20 oz.

Answer 1

Oz: ounce اونس 

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.

https://en.m.wikipedia.org/wiki/Ounce