metric system

Short definition from Wiktionary

Noun

1. 1
   The system of units developed in France in the 1790s and now used worldwide.
2. 2
   The modern version of that system, Système International d'Unités (International System of Units), or SI that is based on the base units of the meter/metre, the kilogram, the second, the ampere, the kelvin, the mole, and the candela.
3. 3
   Any variant of that system that was not codified as SI, such as cgs.