astragal

Astragal, or astragalus in some contexts, is a term with multiple senses across anatomy, archaeology, botany, and architecture. In anatomy, astragalus is another name for the talus, the bone that forms the lower part of the ankle joint. The bone articulates with the tibia and fibula above and with the calcaneus below, enabling the hinge-like motions of the foot.

In archaeology and the history of games, an astragal refers to the knucklebone used as a gaming piece. Typically the ankle bone of a sheep or goat, astragali were employed in ancient games that resemble dice. The term can be used in the singular or plural forms, depending on whether one bone or several are being described.

In botany, Astragalus is a very large genus of flowering plants in the legume family Fabaceae, commonly known as milkvetches. The genus contains thousands of species, ranging from herbaceous perennials to shrubs, and it is widespread across temperate regions. Some species are used as forage plants, while others have traditional medicinal uses in East Asia; Astragalus membranaceus is among the better-known examples, though a range of species and preparations are involved in such uses.

In architecture and design, an astragal is a slender molding or beading that can separate panels or devices, and it may appear as a decorative strip between panes or door elements. The term reflects historical use of small, bead-like components in decorative work and shares its root with the other senses through classical language.