Cup is a non standard volume measurement unit and used in different measurement systems. Metric cups are slightly larger than the U.S. customary cups. Mostly used in cooking to measure liquid and bulk, dry foods. Depending on what to measure (fluid or dry), cup materials or shapes are usually different (as seen in the pictures at the bottom of the page). It's abbreviated as "c".
Fluid ounce is a volume unit in several measurement systems. It is a commonly used unit in cooking recipes. It's abbreviated as "fl oz". Ounce is also used as a weight unit but to distinguish between these two, volume unit is called fluid ounce. This often causes confusion since sometimes there is a need to convert from a volume unit cup to a weight unit (ounce or grams). This is not possible unless you know the density of the unit that you are converting into. But, if you are wondering how many grams in a cup for butter, sugar, flour and honey, please check the table below that has pre-measured values.