noun
prefixed unit of measurement
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.
古い教科書では、ミリメートルやキログラムを「補助単位」と呼んでいた。
Old textbooks called millimeters and kilograms 'prefixed units of measurement'.
noun
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
ラジアンとステラジアンは、かつてSIの補助単位に分類されていた。
The radian and steradian were once classified as supplementary SI units.
組立単位 refers to derived units formed by combining base units (e.g., m/s²), while 補助単位 historically referred to prefixed or supplementary units.
Compound of 補助 (assistance, supplementary) and 単位 (unit). The term reflects its historical use in measurement systems for units that are not base units.