International system of units

International System of Units (SI) is the modern form of the metric system and is the most widely used system of measurement. It comprises a coherent system of units of measurement built on seven base units, which are the second, meter, kilogram, ampere, kelvin, mole, and candela.

History

The International System of Units was developed from the metric system at the General Conference on Weights and Measures (CGPM) in 1960. The conference, which is held every four to six years, is attended by delegates from many nations, and the decisions made at these conferences are implemented by the International Bureau of Weights and Measures (BIPM).

Base Units

The seven base units used in the SI system are:

• Second (s) - The unit of time
• Meter (m) - The unit of length
• Kilogram (kg) - The unit of mass
• Ampere (A) - The unit of electric current
• Kelvin (K) - The unit of thermodynamic temperature
• Mole (mol) - The unit of amount of substance
• Candela (cd) - The unit of luminous intensity

Derived Units

In addition to the base units, the SI system also includes many derived units, which are formed by combining the base units according to the rules of algebra. Some examples of derived units include the watt (W), which is a unit of power, and the volt (V), which is a unit of electric potential.

Symbols and Prefixes

Each unit in the SI system has a symbol, and these symbols are always written in lowercase, except for those derived from the name of a person, which are capitalized. The SI system also includes a set of prefixes that indicate multiplication or division by a power of ten.

See Also

• Metric system
• Measurement
• Units of measurement

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