Arcus

Part of speech: noun

Pronunciation: /ˈɑɹkəs/

Definitions

1. A term for an arch-shaped anatomical structure such as a bent bone or vessel ; a type of low, shelf-like cloud formation that forms along a gust front ; or the Latin-derived word used for any curve resembling an arc in science or architecture
2. Refers to a bowlike anatomical part in living organisms ; a dramatic, horizontal cloud feature marking storm outflows ; or a general descriptor for arching forms in geometry, art, or ancient language
3. Used for curved structures in biology like bony arches ; a meteorological band-shaped cloud seen at thunderstorms’ edges ; or a name applied to any pronounced convex shape in specialized contexts

Etymology: "Arcus" is the Latin word for a bow, the curved weapon that fires arrows, and English borrowed it directly from that Latin source. Its English sense is a curved structure in the body, most familiar in the "arcus senilis," the grey or white ring that forms around the edge of the cornea in older people, and in the arch-shaped parts of the anatomy the word names. The word is a doublet of "arc" and "arco." These three English and Italian forms all descend from the same Latin noun, but they reached the language by different routes and at different times, so each picked up its own specialised sense. "Arc" took on the geometric meaning of a section of a curve, while "arcus" stayed in the technical vocabulary of anatomy and medicine. The Latin root is distantly related to "arrow," which reflects a shared Indo-European ancestor for words describing bows and the curved shapes associated with them.

Synonyms: arch, arc