The International System of Units (abbreviate SI from the French Le Système International d'Unités) is the modern form of the metric system and is generally a system devised around the convenience of the number 10. It is the world's most widely used system of units, both in everyday commerce and in science. An extensive presentation of the SI units is maintained on line by NIST, including a diagram of the interrelations between the derived units based upon the SI units. Definitions of the basic units can be found on this site, as well as the CODATA report listing values for special constants such as the electric constant, the magnetic constant and the speed of light, all of which have defined values as a result of the definition of the metre and ampere.