noun
internal corner; inside corner
Architectural term for the concave corner where two walls or planes meet; opposite of 出隅 (outside corner).
部屋の入隅に小さな棚を設置した。
I installed a small shelf in the inside corner of the room.
入隅の処理は左官の腕の見せ所だ。
The treatment of internal corners is where a plasterer's skill shows.
出隅 is the external (convex) corner, while 入隅 is the internal (concave) corner.
Compound of 入り (iri, 'entering') + 隅 (sumi, 'corner'). The kanji 入 means 'enter' and 隅 means 'corner', together indicating a receding corner.