| − | Characters for some metric units were created in the late 19th century ({{w|Meiji period}} [[kokuji]]) by composing two characters, one for a base unit, one for a prefix. With 3 base units and 7 prefixes (6 characters, and blank for no prefix), this yields 3×7=21 characters – see [[International System of Units#Chinese characters|Chinese characters for SI units]] for details. These are no longer in common use. | + | Characters for some metric units were created in the late 19th century ({{w|Meiji period}} [[kokuji]]) by composing two characters, one for a base unit, one for a prefix. With 3 base units and 7 prefixes (6 characters, and blank for no prefix), this yields 3×7=21 characters – see [[International System of Units#Chinese characters|Chinese characters for SI units]] for details. These are no longer in common use, and instead one generally writes these with two half-width Latin characters in a single full-width space, as in "km" or "mg". |