The metric system is a system of measurement of decimal units based on the meter. For scientific purposes the SI units of the metric system are adopted. SI (Système Internationale d'Unites) uses seven different fundamental units, the meter, kilogram, second, ampere, kelvin, candela, and mole. There are also two supplementary units, the radian, and the steradian. All other units are derived from these units by multiplication or division.

The basic unit of length is the meter (sometimes spelled metre). The original meter is a metal rod stored in Sèvres, France, and its length initially was defined as a fraction of the circumference of the Earth. The meter is now defined more precisely as the distance that light can travel in a vacuum in 1/299,792,458 of a second. The internationally recognized abbreviation of the meter is m. Meters are divided up into smaller units...