|any decimal system of units based on the metre. For scientific purposes the Système International d'Unités (SI units) is used|
metric system n.
A decimal system of units based on the meter as a unit length, the kilogram as a unit mass, and the second as a unit time.
A system of measurement in which the basic units are the meter, the second, and the kilogram. In this system, the ratios between units of measurement are multiples of ten. For example, a kilogram is a thousand grams, and a centimeter is one-hundredth of a meter. Virtually all countries of the world, except the United States, use the metric system. Among scientists, the metric system is called SI — an abbreviation for Système internationale, which is French for “International System.”