also: みなのか · さんしちにち
noun
21st day after death; 21st day after birth
Buddhist term for the 21st day after a person's death, when a memorial service is often held. Also used for the 21st day after a child's birth, though this usage is less common.
三七日の法要を営む。
Hold a memorial service on the 21st day after death.
三七日のお祝いをする。
Celebrate the 21st day after birth.
Refers to the 49th day after death, a more significant memorial day in Buddhism, whereas 三七日 marks the 21st day.
From 三 (three) + 七 (seven) + 日 (day), literally 'three-seven day', i.e., the 21st day. The reading みなぬか is a native Japanese reading (kun'yomi) of the characters.