On drawings, abbr. for architect, architecture, or architectural.

A construction that spans an opening; usually curved; often consists of wedge-shaped blocks (voussoirs) having their narrower ends toward the opening. Arches vary in shape, from those that have little or no curvature to those that are acutely pointed. For special types of arches, see acute arch,
anse de panier, arrière-voussure, back arch, basket-handle arch, bell arch, blind arch, camber
arch, catenary arch, cinquefoil arch, compound arch, cusped arch, diminished arch, discharging arch, Dutch arch, elliptical arch, equilateral arch, flat arch, Florentine arch, foil arch, French arch, garden arch, gauged arch, Gothic arch, horseshoe arch, inverted arch, jack arch, keel arch, keystone arch, lancet arch, Mayan arch, memorial arch, miter arch, Moorish arch, ogee arch, pointed arch, Queen Anne arch, raking arch, rampant arch, rear arch, relieving arch, round arch, rowlock arch, safety arch, sconcheon arch, secondary arch, segmental arch, semicircular arch, semielliptical arch, shouldered arch, skew arch, straight arch, three-centered arch, transverse arch, trefoil arch, triangular arch, triumphal arch, Tudor arch, two-centered arch