supplementary units in SI

In SI, 1960 – 1995, a class of units whose only members were the radian and steradian.

The class of supplementary units was created in 1960 by the 11th CGPM (Resolution 12) to cover those units which are neither base units nor derived from base units (derived units). In 1969 the CIPM, “considering that Resolution 12...has provoked discussions,” formally declared that “the name ‘supplementary units’ is given to SI units for which the General Conference declines to state whether they are base units or derived units.”1

In 1980, taking into account the advice of two committees, the CIPM refined the concept of supplementary units (Resolution 1, CI-1980), deciding “to interpret the class of supplementary units in the International System as a class of dimensionless derived units for which the CGPM allows the freedom of using or not using them in expressions for SI derived units.”2

In 1995, the 20th CGPM eliminated this class.

1.
“International System of Units: Rules for the application of Resolution 12 of the 11th CGPM (1960)”
in Procès Verbaux, volume 37, page 30. Recommendation 1.

2.
“SI Supplementary Units (radian and steradian).”
in Procès Verbaux, volume 48, page 24.

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