内壁

例句：

1. 1. The room has a smooth inner wall.
   这个房间有一个光滑的内壁。
2. 2. The engineer studied the inner wall of the building.
   工程师研究了大楼的内壁。
3. 3. The inner wall is made of bricks.
   内壁是由砖块制成的。