函かん蓋がい

noun

box and cover; container and lid

A rare literary or technical term referring to a box together with its lid, or metaphorically to things that fit together perfectly. Not used in everyday conversation.

• 「函かん蓋がい相そう称しょう」という四よ字じ熟じゅく語ごで、函はこと蓋ふたがぴったり合あうように、物もの事ごとがうまく調ちょう和わすることを表あらわす。

  The four-character idiom 函蓋相称 expresses that things harmonize well, just as a box and its lid fit perfectly together.