The short ton (S/T) is a unit of mass equal to 2,000 lb (exactly 907.18474 kg). In the United States it is often called simply ton without distinguishing it from the metric ton (or tonne, 1,000 kilograms) or the long ton (2,240 pounds, exactly 1,016.0469088 kg) —rather, the other two are specifically noted. There are, however, some U.S. applications for which unspecified tons normally means long tons (for example, Navy ships) or metric tons (world grain production figures).
Both the long and short ton are defined as 20 hundredweights, but a hundredweight is 112 pounds (which is equal to 8 stone) in the Imperial system (long or gross hundredweight) and 100 pounds in the U.S. system (short or net hundredweight).
The spelling tonne is from Gallic and French. The term applied to the barrel of the largest size. In Old English the spelling was tunne, "cask" - a full cask about a metre high could easily weigh a tonne. The antiquated British wine cask volume measurement tun is close to a metric tonne in weight as it defines about 954 litres which for most liquids amounts to as many kilograms.
A short ton–force is 2,000 pounds-force (8,896 newtons).