noun
imprisonment (1-3 years; third most severe ritsuryō punishment)
Historical term for a specific penal sentence under the ritsuryō system. The punishment involved imprisonment with labor for one to three years, ranking below death and exile.
See also: 五刑
律令制では、徒は五刑の一つで、懲役を伴う刑罰だった。
Under the ritsuryō system, 徒 was one of the five punishments, involving imprisonment with labor.
The reading ず is a Sino-Japanese reading of the kanji 徒, used in the historical legal term for imprisonment. The exact derivation is uncertain; the kanji is conventionally associated with the meaning of penal servitude in this context.