arch

An arch is a curved structural element that spans an opening and transfers loads to its supports primarily through compression. It is composed of wedge-shaped blocks called voussoirs arranged along a curved profile, with a central keystone that locks the curve in place. The imposts or springers mark the start of the curve and transmit load to the abutments, which resist the outward thrust generated by the arch. By directing weight along a curved path, arches enable wider spans and taller openings than lintels.

Arches come in several forms. Semicircular arches, or Roman arches, have a full 180-degree sweep. Pointed arches, characteristic of Gothic architecture, rise more sharply and allow taller structures. Segmental arches use a shallower curve, producing lower thrust; horseshoe arches widen the leg of the curve; elliptical and parabolic arches offer alternative profiles suitable for various aesthetic and structural needs.

Materials range from traditional cut stone and brick to modern reinforced concrete and steel. Construction relies on precise cutting and fitting of voussoirs, accurate abutments, and, in many cases, temporary supports that are removed after the keystone is set. The arch’s strength lies in compression; tensile forces are limited by hinge points and by the supports at its ends.

Historically, arches appeared in ancient Mesopotamian and Persian architecture and were perfected by the Romans. They underpin many bridges, aqueducts, vaults, and doorways throughout classical and medieval architecture, and remain a staple in modern civil engineering and design. In computing, Arch can also refer to Arch Linux, a rolling-release Linux distribution.