Siemens (unit)

Siemens (unit)

The siemens (SI unit symbol: S) is the unit of electric conductance and electric admittance in the International System of Units (SI). Its symbol, "S" (upper case), should not be confused with the SI symbol "s" (lower case) which is used for second. Conductance and admittance are the reciprocals of resistance and impedance respectively, hence one siemens is equal to the reciprocal of one ohm, and is also referred to as the mho. The 14th General Conference on Weights and Measures approved the addition of the siemens as a derived unit in 1971.

The unit is named after Ernst Werner von Siemens. As with every SI unit whose name is derived from the proper name of a person, the first letter of its symbol is upper case (S). When an SI unit is spelled out in English, it should always begin with a lower case letter (siemens), except where any word would be capitalized. In English, the same form siemens is used both for the singular and plural.