noun
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.
江戸時代、大名の正室はしばしば人質として江戸に住まわされた。
In the Edo period, the legal wives of daimyo were often made to live in Edo as hostages.
noun
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)
この武家屋敷では、正室で来客をもてなした。
In this samurai residence, guests were entertained in the formal reception room.
noun
Rare historical usage; may appear in old texts or genealogical records. Not used in modern Japanese for this meaning.
古文書では、「正室」が嫡男を指す例がまれに見られる。
In old documents, there are rare instances where 正室 refers to the heir.
表座敷 is a more common term for a formal reception room, while 正室 in this sense is more specific to traditional samurai residences.
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.