The plural of arch is arches.
An arch is a curved structural element that spans an open space and supports the weight above it. It is often used in architecture and engineering to create strong and stable structures, such as bridges, doorways, and vaulted ceilings. Arches distribute the weight evenly along their curved shape, allowing them to withstand significant loads and pressures. They can be made of various materials, including stone, brick, concrete, and metal. Arches have been used for centuries and are admired for their aesthetic appeal and structural ingenuity.