a curved structure that supports the weight of something above it, such as a bridge or the upper part of a building 拱（支撑如桥梁或房屋上部的弧形结构） 
a bridge with three arches 有三个拱的桥。 Homeless people slept under the railway arches. 无家可归的人睡在铁路拱桥下面。
Oxford Collocations Dictionaryadjective- pointed
- round
- rounded
- …
- build
- erect
- form
- …
- beneath an/the arch
- through an/the arch
- under an/the arch
- …
a structure with a curved top that is supported by straight sides, sometimes forming an entrance or built as a monument 拱门 
Go through the arch and follow the path. 穿过拱门沿小径往前走。 Marble Arch is a famous London landmark. 大理石拱门是伦敦著名的地标。
Extra ExamplesThis huge triumphal arch was erected at the beginning of this century. 这座巨型凯旋门是本世纪初建造的。 We rode under the arch. 我们在拱门下骑自行车。
Oxford Collocations Dictionaryadjective- pointed
- round
- rounded
- …
- build
- erect
- form
- …
- beneath an/the arch
- through an/the arch
- under an/the arch
- …
the raised part of the foot formed by a curved section of bones 足背；足弓 
anything that forms a curved shape at the top 拱形；拱形物 the delicate arch of her eyebrows 她那弯弯的柳眉 The branches of the trees formed an arch over the bench. 树枝交错，在长椅上方形成一个拱形。
Oxford Collocations Dictionaryadjective- pointed
- round
- rounded
- …
- build
- erect
- form
- …
- beneath an/the arch
- through an/the arch
- under an/the arch
- …
Word Originnoun Middle English: from Old French arche, based on Latin arcus ‘bow’.