Demilune

Demilune, from the French demi-lune meaning half-moon, is a term used in several fields to describe a shape or form that resembles a semicircle or crescent. The sense most often encountered is geometric, but domain-specific uses are common in architecture, military fortification, and anatomy.

In architecture and decorative arts, a demilune denotes a semicircular feature such as a niche, window, pediment, or other curved element. It refers to a half-mmoon silhouette that may be used decoratively or functionally to modulate light, space, or emphasis within a structure. The term appears in the description of various classical and medieval architectural details and schemes.

In military architecture, a demilune refers to a half-moon–shaped outwork or redoubt placed in front of a fortress wall. Demilune fortifications provide protective fire along the curtain and improved coverage of approaches, often forming a projecting semicircular or crescent-shaped defensive element that complements the main enceinte.

In histology, demilune describes crescent-shaped serous cells that cap mucous acini in certain salivary glands. These serous demilunes (also called demilune cells) are characteristic of mixed glands such as the submandibular and sublingual glands, where serous tissue partially encircles mucous units.

See also: lunette.