Pointed
A pointed arch consists of two ("two-centred arch") or more circle segments culminating in a point at the top. Early examples occur at Qasr Ibn Wardan in Syria (AD 561–564), and the form subsequently became widespread in Islamic architecture. It was used in Western Europe in the second half of the 11th century, including at Monte Cassino and Cluny Abbey, and later became prominent in Gothic architecture.
The advantages of a pointed arch over a semicircular one are flexible ratio of span to rise and lower horizontal reaction at the base. This innovation allowed for taller and more closely spaced openings, which are typical of Gothic architecture.
Equilateral arch is the most common form of the pointed arch, with the centers of two circles forming the intrados coinciding with the springing points of the opposite segment. Together with the apex point, they form an equilateral triangle, thus the name. If the centers of circles are farther apart, the arch becomes a narrower and sharper lancet arch that appeared in France in the Early Gothic architecture (Saint-Denis Abbey) and became prominent in England in the late 12th and early 13th centuries (Salisbury Cathedral). If the centers are closer to another, the result is a wider blunt arch.
The intrados of the cusped arch (also known as multifoil arch, polyfoil arch, polylobed arch, and scalloped arch) includes several independent circle segments in a scalloped arrangement. These primarily decorative arches are common in Islamic architecture and Northern European Late Gothic, can be found in Romanesque architecture. A similar trefoil arch includes only three segments and sometimes has a rounded, not pointed, top. Common in Islamic architecture and Romanesque buildings influenced by it, it later became popular in the decorative motifs of the Late Gothic designs of Northern Europe.
Each arc of an ogee arch consists of at least two circle segments (for a total of at least four), with the center of an upper circle being outside the extrados. The English Decorated style, French Flamboyant, Venetian, and other Late Gothic styles made frequent use of the ogee. European examples date back to the west front of St Mark's Basilica in Venice (around 1250) and the Eleanor crosses in England (from 1291). Ogee arch is also known as reversed curve arch, occasionally also called an inverted arch. A nodding ogee has an apex that projects forwards from the wall. In early 14th-century England, where it was widely used, it usually served no structural purpose. Examples include the pulpitum of Southwell Minster and the Lady Chapel of Ely Cathedral.
Each arc of a four-centred arch is made of two circle segments with distinct centers; usually the radius used closer to the springing point is smaller with a more pronounced curvature. Common in Islamic architecture (Persian arch), and, with upper portion flattened almost to straight lines (Tudor arch), in the English Perpendicular Gothic.A keel arch is a variant of four-centred arch with haunches almost straight, resembling a section view of a capsized ship. Popular in Islamic architecture, it can be also found in Europe, occasionally with a small ogee element at the top, so it is sometimes considered to be a variation of an ogee arch.
Curtain arch (also known as inflexed arch, and, like the keel arch, usually decorative) uses two (or more) drooping curves that join at the apex. Utilized as a dressing for windows and doors primarily in Saxony in the Late Gothic and early Renaissance buildings (late 15th to early 16th century), associated with Arnold von Westfalen. When the intrados has multiple concave segments, the arch is also called a draped arch or tented arch. A similar arch that uses a mixture of curved and straight segments or exhibits sharp turns between segments is a mixed-line arch (or mixtilinear arch). In Moorish architecture the mixed-line arch evolved into an ornate lambrequin arch, also known as muqarnas arch.
