legal wife; principal wife
Historical term for the official wife of a noble or samurai, as opposed to a concubine (側室). In modern contexts, it may be used metaphorically or in historical discussions.
In the Edo period, the legal wives of daimyo were often made to live in Edo as hostages.
formal reception room; guest parlor
In traditional Japanese architecture, the main room for receiving guests, often the most formal space in a residence. Compare 表座敷 (おもてざしき).
See also: 表座敷 (おもてざしき)
In this samurai residence, guests were entertained in the formal reception room.
Rare historical usage; may appear in old texts or genealogical records. Not used in modern Japanese for this meaning.
In old documents, there are rare instances where 正室 refers to the heir.
proofreading room; proofroom
Composed of 正 (correct, main) and 室 (room, wife). The meaning 'legal wife' derives from the idea of the principal wife's quarters, and by extension the wife herself. The 'reception room' sense is a literal reading of the characters. The rare 'heir' sense may be an extension of the 'principal wife' meaning, as the heir was typically the son of the legal wife.