Arch - Oxford Definition

A construction of a block of materials in a curved form used as a support, for example of a bridge, floor, or roof. The simplest arches are semicircular. Pointed arches appeared in Moorish and Gothic architecture. The following are the most commonly encountered types of arch: a basket or three-centred arch (French anse de panier) has a curve that resembles the handle of a basket, and is formed by a segment of a large circle continued left and right by two segments of much smaller circles; a drop arch is pointed with a span greater than its radii; an elliptical arch is a half ellipse with its centre on the springing line; a false arch is formed by progressively cantilevering or corbelling from the two sides with horizontal joints; a four-centred or depressed arch is a late medieval form—a pointed arch of four arcs springing from centres on the springing line; a horseshoe arch is often found in Islamic buildings and can be either a pointed or round horseshoe; a lancet arch is pointed, with radii much larger than the span; an ogee arch is pointed and usually of four arcs, the centres of two inside the arch, the other two outside, this produces a compound curve of two parts, one concave and the other convex, introduced c.1300 it was popular throughout the late Middle Ages, especially in England in the early 14th century; a relieving or discharging arch is a strengthening device placed in the wall above an arch or any opening to protect it from much of the weight that would otherwise fall on it; a shouldered arch consists of a lintel connected with the jambs of a doorway by corbels; a stilted arch is one with its springing line raised by vertical piers above the impost level; a strainer arch is one inserted across a nave or an aisle to prevent the walls from leaning; a Tudor arch is a late medieval pointed arch.