A cusp is a pointed projection formed at the junction of two curved arcs in Gothic tracery, creating the characteristic pointed lobes seen in windows, arches, and decorative panels. Cusps are one of the most recognizable ornamental features of Gothic architecture.
Applications
Cusps are integral to Gothic tracery, the decorative stonework that divides and ornaments window openings, blind arcades, and panel designs. When two arcs of a multi-lobed (foiled) opening meet, the inward-pointing projection at their intersection is the cusp. The number of cusps determines the type of foil: a trefoil has three cusps, a quatrefoil has four, a cinquefoil has five, and so on.
The development of cusped tracery is closely linked to the evolution of Gothic window design. In the Early English period (13th century), lancet windows gave way to plate tracery, where simple geometric openings were cut from flat stone panels. As tracery became more sophisticated in the Decorated and Rayonnant periods, cusps became more refined and elaborate. Bar tracery, in which slender stone mullions and arcs create intricate patterns, allowed for increasingly complex cusped designs.
Structurally, cusps serve no load-bearing function. Their role is purely decorative, breaking up the curves of arcs into smaller, more visually interesting segments. The pointed forms create patterns of light and shadow that enrich the appearance of windows, especially when seen against stained glass or the sky.
Beyond windows, cusps appear in a variety of architectural elements. They decorate blind arcading on walls, enrich the profiles of pointed arches, and ornament screen walls, choir screens, and canopied niches. In the Flamboyant Gothic style of the 15th century, cusps became especially elaborate, with secondary cusps (sub-cusps) creating flame-like patterns that gave the style its name.
Cusps are also found in Islamic architecture, where multi-lobed arches with cusped profiles are a common decorative feature, particularly in Moorish buildings in Spain and North Africa.
Related terms
- Tracery
- Foil (trefoil, quatrefoil)
- Mullion
- Gothic arch
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