6. Defining units

The seven basic SI units have been defined by the General Conference on Weights and Measures. These definitions are given below, under the corresponding headings.

Derived SI units are defined by their expression in terms of base units.

Any other form of definition, more or less explicit, is not, strictly speaking, a true definition of the derived unit, but a commentary, an explanation of the nature of one or more quantities for which it is the unit of measurement. However, it should not be forgotten that the same unit can be assigned to all quantities with the corresponding dimension. It is this characteristic...