This Standard has been prepared as a guide for the application of the International System of Units (SI). Information is included on SI units, recommended application of multiples and sub-multiples of the units, up-to-date terminology concerning the names of quantities, conversion factors that relate the SI to other systems of units, conversion and rounding of data, and dual dimensioning.
The interpretation of clauses depends on the correct interpretation of the words shall, should, and may. Shall is mandatory; should is recommendatory; may is permissive.
The Système international d'unités (SI) is a system of units that has evolved into its present form in response to a wide range of requirements. The base units of the system were chosen as a small number of convenient and acceptable units from which other units of the system could be derived coherently (ie, by the processes of multiplication or division of base units, using one as the only numerical factor).
Note: The usage of the word base is international and does not imply that a base unit is basic or fundamental, or more fundamental than other units of the system.