Noun

1. In the International System of Units, the base unit of mass; the mass of a specific cylinder of platinum-iridium alloy kept at the International Bureau of Weights and Measures in France. Symbol: kg
2. Hence, the unit of weight such that one-kilogram mass is also a one-kilogram weight.

Usage notes

The use of the kilogram as a unit of weight is somewhat imprecise, as weight can change while mass remains constant. The weight of a one-kilogram mass will depend on its location, which will impact the pull of gravity. It is therefore frequently proscribed, but is nonetheless in wide use (e.g., a person's weight in kilograms). (The same imprecision and proscription also occur with many other words pertaining to weight and mass, such as the verb .)