補助単位
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Meanings
1
prefixed unit of measurement
obsolete term
Obsolete term for a unit formed by adding a prefix to a base unit, such as millimeter or kilogram. In modern Japanese, 接頭語付き単位 or simply 単位 with the prefix is more common.
Old textbooks called millimeters and kilograms 'prefixed units of measurement'.
2
supplementary SI unit
Specifically refers to the radian and steradian in the International System of Units. This usage is technical and may be encountered in older metrology contexts; modern Japanese often uses 補助計量単位 or simply ラジアン and ステラジアン.
See also: 組立単位
The radian and steradian were once classified as supplementary SI units.