Units, conversion factors and constants

Abstract

The name International System of Units (SI) has been adopted by the Conférence Génerale des Poids et Mésures for a coherent system of units of measurement. The system consists of seven basic units (see 2.1.1) and two supplementary units (see 2.1.2). Frequently derived units have been given special names and are summarized in 2.1.3. Other derived units are listed in 2.1.4. A convenient way to indicate multiples and fractions of the units in powers of ten is achieved by the use of proper prefixes which can be found in 2.1.5. Units constructed using these prefixes are SI units. Multiples and decimal fractions of SI units which have their own names are listed in 2.1.6. These units are not official SI units and their use is discouraged. Units of other systems which are defined exactly in terms of SI units are listed in 2.1.7.