si unit

(noun) a complete metric system of units of measurement for scientists; fundamental quantities are length (meter) and mass (kilogram) and time (second) and electric current (ampere) and temperature (kelvin) and amount of matter (mole) and luminous intensity (candela). Synonyms: Systeme International d'Unites, Systeme International, SI system, SI, SI unit, International System of Units, International System. Example: "Today the united states is the only country in the world not totally committed to the systeme international d'unites."