SI, aka Système international, is a notation created in 1960.
The International System of Units (abbreviated as SI, from the French Système international (d'unités)) is the modern form of the metric system, and is the most widely used system of measurement. It comprises a coherent system of units of measurement built on seven base units and a set of twenty prefixes to the unit names and unit symbols that may be used when specifying multiples and fractions of the units. The system also specifies lowercase names for 22 derived units. Read more on Wikipedia...