colonnade

colonnade, arcade, arcature, portico, peristyle are discriminable as used in architecture.

A colonnade is a row of columns (typically on the outside of a building) spaced at regular intervals and carrying an architrave or horizontal member lying directly across their capitals, so that the opening between each pair of columns is square-topped. Colonnade is usually applied not only to the columns but to the entire structure consisting of columns, roof, and pavement or to the space which they enclose. The word is used especially in reference to classical architecture.

An arcade is a long series of arches with their supporting columns and piers together with the other members that complete the structure as an architectural feature. An arcade may be either inside or outside of a building; it may be a purely decorative feature or a means of admitting light and air. When purely decorative, the spaces between the arches and the piers may be filled in (sometimes providing niches for statues); this type of arcade is also called an arcature.

An arcade may take the place of an outer wall (as of a gallery or cloister). Arcade is used especially of types of architecture (as the late Romanesque and the Gothic) in which the arch is an essential feature. Portico and peristyle are used in reference to architectural features employing the colonnade. When the colonnade extends across, or nearly across, one side of a building and serves as an entrance, it is called a portico; when it is continued so as to extend along three or, usually, all four sides of a building, it is called a peristyle,