Tonnage

Tonnageis a measure of the capacity of a ship, and is commonly used to assess fees on commercialshipping. The term derives from the taxation paid on tuns or casks of wine. In modern maritime usage, "tonnage" specifically refers to a calculation of the volume or cargo volume of a ship. Although tonnage (volume) should not be confused with displacement (the actual mass of the vessel), the long ton (or imperial ton) of 2,240 lb is derived from the fact that a "tun" of wine typically weighed that much.