A catenary arch is the ideal structural arch form:

• Shape = the curve formed by a hanging chain or rope (catena = chain in Latin), inverted.
• Under uniform self-weight loading, a catenary arch carries loads purely in compression along its axis — no bending, no tension.
• Structurally optimal — zero bending moment throughout.
• Famous example: Antonio Gaudí used catenary arches in Sagrada Família; Eero Saarinen's Gateway Arch (St. Louis) is a weighted catenary.

Round arches and pointed arches do experience bending under non-uniform loads.