The cup is a unit of volume in the US customary unit system with the symbol cup.
It is equal to 1/2 US customary pint, 1/4 US customary quart and 1/16 US customary gallon. it is also equal to 236.5882365 millilitres.
Used primarily for cooking - the cup was adopted and established as a recognised unit of measure as it could be used by almost anyone in any kitchen. Due to the slight variants in design and size, it is rarely used as an accurate measure for important or critical materials, however it does represent a specific amount and can be used across many recipes to indicate what is needed.
The imperial fluid ounce is a unit of volume from the imperial unit system and uses the symbol fl oz.
1 imperial fluid ounce is equal to 28.41306 ml. It is also equivalent to 0.9607599 US fl oz.
The imperial gallon was defined in Britain by Parliament in 1824 and established as ten pounds of water at a normal temperature. This was split into 4 quarts, each quart into 2 pints, each pint into 4 gills and each gill into 5 ounces.
Therefore; 1 imperial fluid ounce is equal to 1/20 imperial pint, 1/40 imperial quart and 1/160 imperial gallon.