An Etymological Dictionary of Astronomy and Astrophysics

1. General: Something shaped like a → curve or → arch.
   

2. Math.: A → segment of a → circle.
   

3. Electricity: A continuous luminous → discharge across a gap between two → electrodes, as in an arc lamp. → electric arc.
   

4. Astro.: The apparent path of a celestial body above and below the horizon.

Etymology (EN): M.E. ark, from M.Fr. arc “bow,” from L. arcus “bow, arch” (cf. Goth. arhwazna “arrow,” O.E. earh), PIE *arqu- “bowed, curved.”

Etymology (PE): Kamân “arc, bow” from Mid.Pers. kamân, related to xam “curve,” cf. Breton kamm “curved, bent,” Gk. kampe “a corner, a joint,” L. campus “a field,”
Lith. kampus “corner,” PIE *kamb- “to bend, crook.”