capacityThe amount of liquid (or other pourable substance) that an object can hold when it's full.
cupA unit of capacity equal to 8 fluid ounces.
fluid ounce

A unit of capacity equal to  of a cup. One fluid ounce of water at 62°F weighs about one ounce.

gallonA unit equal to 4 quarts, or 128 fluid ounces.
pintA unit of capacity equal to 16 fluid ounces, or 2 cups.
quartA unit of capacity equal to 32 fluid ounces, or 4 cups.