Ton is the name of any one of several units of measure. It has a long history and has acquired several meanings and uses.

Mainly it describes units of mass. Confusion can arise because ton can mean

• the long ton, which is 2,240 pounds (1,016.0469088 kilograms)
• the short ton, which is 2,000 pounds (907.18474000 kilograms)
• the tonne, also called the metric ton, which is 1,000 kilograms (about 2,204.6226218 pounds) or 1 megagram.

Its original use as a measurement of volume has continued in the capacity of cargo ships and in terms such as the freight ton and a number of other units, ranging from 35 to 100 cubic feet (0.99 to 2.83 m³) in capacity. Recent specialized uses include the ton as a measure of energy and as a means of truck classification. It can also be used as a unit of energy, or in refrigeration as a unit of power, sometimes called a ton of refrigeration.

Because the ton (of any system of measuring weight) is usually the heaviest unit named in colloquial speech, its name also has figurative uses, singular and plural, informally meaning a large amount or quantity, or to a great degree, as in "There's a ton of bees in this hive", "We have tons of homework", and "I love you a ton."