Emily Dickinson Lexicon

ARCH, n. [See Arc.]

1. A segment or part of a circle. A concave or hollow structure of stone or brick, supported by its own curve. It may be constructed of wood, and supported by the mechanism of the work. This species of structure's much used in bridges. A vault is properly a broad arch. – Encyc.
2. The space between two piers of a bridge, when arched; or any place covered with an arch.
3. Any curvature in the form of an arch.
4. The vault of heaven, or sky. – Shak. Triumphal arches are magnificent structures at the entrance of cities, erected to adorn a triumph and perpetuate the memory of the event.