metric system
decimal system of units that uses the metre as the basis for its unit of length
International System of Units
system of units, based on the International System of Quantities, their names and symbols, including a series of prefixes and their names and symbols, together with rules for their use (International Vocabulary of Metrology)
gravitational metric system
system of units based on the three base quantities length, time and force with base units metre, second and kilopond