A structure,especially one of masonry,forming the curved,pointed,or flat upper edge of an open space and supporting the weight above it,as in a bridge or doorway.

• 拱形结构，一种石造建筑结构，构成开放空间的弯曲的、有尖顶的或平坦的上边缘，支撑其上重量，如在桥或门上的。