système international (SI)
Système International(SI) is the international system of units in which the definitions of physical units are laid down. The SI system of units has evolved from the metric MKS system of units and has been anchored in Germany since 1970 in the Law on Units in Metrology.
The SI system of units comprises the seven basic quantities length, mass, time, current, temperature, quantity of matter and luminous intensity. The basic units are based on reproducible natural constants and cannot be derived from other units. On the other hand, all other physical and electrical quantities can be derived from the base units, such as area, density, frequency, energy, power, voltage, resistance, field strength, capacitance, inductance, etc. All units are prefixed for practical use, forming a decimal multiple.
The basic quantities of the system of units are implemented and monitored in Germany by the Physikalisch-Technische Bundesanstalt(PTB) in Braunschweig. In addition to the SI system of units, there is also the MKS system of units, which stands for meter, kilogram, second, and the cgs system of units for small units.