側室|そくしつsokushitsu[0]heiban (flat)

1. nounconcubine (of a noble)

• Synonym妾めかけWrittenWritten/formal; an old-fashioned word for a concubine, now little used. 「側室」 specifically denotes a noble or daimyo's concubine.
• Related二号にごうCasualColloquial; a popular, jocular term for a mistress. 「側室」 is the historical, formal designation.
• Related情婦じょうふWrittenWritten/formal; a lover a man keeps besides his wife, and more modern in feel than 「側室」.
• Related二号さんにごうさんCasualColloquial; a politer way of saying 「二号」, though still jocular.
• Related囲い者かこいものCasualColloquial; a woman a man supports financially, somewhat old-fashioned.
• Related囲い女かこいおんなCasualColloquial; a kept woman, synonymous with 「囲い者」.
• Related隠し女かくしおんなCasualColloquial; a mistress kept hidden from one's wife; rarely used.
• Antonym正室せいしつWrittenWritten/formal; the lawful wife of a noble, standing opposite a 「側室」.

For the concubine of an Edo-period daimyo or noble, use 「側室」; his principal wife is 「正室」. A modern lover is 「愛人」, colloquially 「二号」; a woman a man keeps is 「囲い者」.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 嗣子しし以外いがいまたは次男じなん以下いかの男子だんし。
2. 貴人きじんのめかけ。
3. 副室ふくしつ。