The word "拱桥" is formed by combining the character "拱" (gǒng), which means "arch" or "to arch", with the character "桥" (qiáo), which means "bridge". In this compound, "拱" acts as a modifier that describes the shape or structure of the "桥", directly specifying it as an arched bridge. Thus, the word is constructed through the semantic juxtaposition of two meaningful characters to denote a specific type of bridge.