kilogram [L18th] At the time of the French Revolution of 1789 different regions of France had different standards of weights and measures, which made trade difficult. To rationalize this, a set of standard units of weight was developed in France in the 1790s by a group of scientists commissioned by the National Convention. A unit based on the mass of a cubic decimetre of water was officially defined as a kilogramme in 1795. Kilogram was formed by combining kilo- derived from Greek kilio ‘thousand’ and -gram, via Latin from Greek gramma ‘small weight’. The metric system is based on using the combining forms kilo-, deca- from Greek deka ‘ten’, deci- shortened from Latin decimus ‘tenth’, centi- (see hundred), and milli- (see million), already combining forms in Latin meaning ‘a hundreth’ and ‘a thousandth’. The meter [L18th] was originally meant to be one ten-millionth of the length of a quadrant of the meridian, although the standard has changed since.