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International System of Units, SI; Système Internationale d’Unités
All systems of weights and measures, metric and non-metric, are linked through a network of international agreements supporting the International System of Units.

The International System is called the SI, using the first two initials of its French name Système International d'Unités.

The primary agreement is the "Treaty of the Meter" or the Convention du Mètre, signed in Paris on May 20, 1875.

Forty-eight nations have signed the treaty, including all the major industrialized countries. The United States is a charter member of the metric club, having signed the original document back in 1875.

Each SI unit is represented by a symbol, not an abbreviation. The use of unit symbols is regulated by precise rules.

These symbols are the same in every language of the world; however, the names of the units themselves vary in spelling according to national procedures; therefore, it is correct for Americans to write meter and Germans to write Meter, and it is also correct for the British to write metre, Italians to write metro, and Poles to write metr.

There is no official spelling of the SI units; however, the SI does provide the names, the definitions, and the symbols of the units which must be followed even when the spellings are different as shown below.

The fundamental SI unit of length has numerous spellings

  • meter (American English, Danish, Dutch, German, Hungarian, Norwegian, Slovak, and Swedish)
  • metr (Czech, Polish, Russian, Ukrainian)
  • metras (Lithuanian)
  • metre (British, Australian, Canadian and New Zealand English; French)
  • metri (Finnish)
  • metro (Basque, Italian, Portuguese, Spanish)

A list of elements associated with the International System of Units (SI)

  • ampere (unit of measurement)
  • are (unit of area measurement)
  • atomic second
  • candela (cd) (SI unit of measurement)
  • centimeter (cm) (unit of measurement)
  • coulomb (unit of energy measurement)
  • farad (unit of measurement)
  • gram (gm or g) (measurement)
  • hectare (unit of measurement)
  • henry (unit of energy measurement)
  • hertz (unit of measurement)
  • joule (unit of energy measurement)
  • kelvin (K) (unit of measurement)
  • kilogram (kg) (unit of measurement)
  • kilometer (km) (unit of measurement)
  • liter (l) (unit of measurement)
  • lumen (unit of energy measurement)
  • lux (unit of energy measurement)
  • megohm (electronics)
  • meter (m) (measurement)
  • metric ton (unit of weight)
  • micrometer (unit of measurement)
  • millimeter (mm) (unit of measurement)
  • mole (chemistry)
  • nanometer (unit of measurement)
  • nanotesla (physics)
  • newton (unit of measurement)
  • ohm (unit of energy measurement)
  • pascal (Pa ) (unit of energy measurement)
  • second (unit of time)
  • siemens (S) (unit of energy measurement)
  • tesla (unit of energy measurement)
  • unit (measurement)
  • volt (unit of measurement)
  • watt (unit of measurement)
  • weber (unit of measurement)

Compiled partly from information located at the
Encyclopedia Britannica on line.
This entry is located in the following unit: Measurements and Mathematics Terms (page 7)