A chaitya arch, also called a chaitya window or a gavaksha, is a horseshoe-shaped arch motif whose curved profile derives from the barrel-vaulted facade opening of an actual rock-cut chaitya hall, the arched window that let daylight fall onto the stupa housed at the hall's far end. As a decorative motif, rather than a real structural opening, the chaitya arch went on to have a far longer architectural life than the chaitya hall form it originally described, appearing in miniature, repeated form as a decorative band framing niches, doorways, windows and the tiers of temple towers across a huge range of later South and Southeast Asian religious architecture, Buddhist and, eventually, Hindu alike.
In its miniaturized decorative use the motif is often stacked or repeated in rows, sometimes housing a small carved face or figure peering out from within each individual arch, a treatment especially common on the shikhara towers of North Indian Hindu temples and on Buddhist stupa and chaitya hall facades across South and Southeast Asia. Because the motif is purely ornamental in most of its later uses, its presence on a building says nothing about whether that building actually contains a barrel-vaulted hall; it survives as a decorative echo of a specific real architectural form long after that form itself became rare.