An arcade is a succession of contiguous arches, with each arch supported by a colonnade of columns or piers. Exterior arcades are designed to provide a sheltered walkway for pedestrians; they include many loggias, but here arches are not an essential element. An arcade may feature arches on both sides of the walkway. Alternatively, a blind arcade superimposes arcading against a solid wall.

An arch is a curved vertical structure spanning an open space underneath it. Arch can either support the load above it or perform a purely decorative role. The arch dates back to fourth millennium BC, but became popular only after its adoption by the Romans in the 4th century BC.