The ton is a unit of measure. It has a long history and has acquired a number of meanings and uses over the years. It is used principally as a unit of weight. Its original use as a measurement of volume has continued in the capacity of cargo ships and in terms such as the freight ton. Recent specialized uses include the ton as a measure of energy and for truck classification. It is also a colloquial term, “ton” (any definition) is the heaviest unit of weight typically used in colloquial speech. It is also used informally to mean a large amount of something, material or not.