The metric system was proposed in 1670 by French clergyman Gabriel Mouton. Mouton proposed a base-ten system of measurement in which the basic unit of length would be the milliare, a distance equal to one minute of arc along a meridian (one ten-millionth of the distance from the equator to a pole). In 1875 a group of European nations collectively adopted the concept. The unit of length was named the meter from the Greek word metron, which means "measure", in the sense of a portion or allotment.
Until 1960 a marked platinum bar, kept by international agreement in a special vault in France, was used as the standard length for a meter. In 1960 it was defined more exactly as 1,650,763.73 wavelengths of the radiation of krypton 86. In 1983 the meter was again redefined as 1/299,792,458 of the distance light travels in a vacuum in one second.