A dome is a space structure covering a more or less square or circular area. The best known example is the dome of revolution, and it is one of the earliest of the shell structures. Excellent examples are still in existence that were built in Roman times. They are formed by a surface generated by a curve of any form revolving about a vertical line. This surface has double curvature and the resulting structure is much stiffer and stronger than a single curved surface, such as a cylindrical shell. The simples dome of revolution is a portion of a sphere. However, other curves are also satisfactory, such as the ellipse, the parabola, other conic sections, or random curves.

Typical profiles for domes are shown later in the chapter and there are an infinite variety of possible shapes, each suitable for a particular purpose. Parts of domes of revolution, square or polygonal in plan with portions of the shell removed, are also considered in this chapter as domes of revolution. Their structural action is much more complex than the dome circular in plan.