Latin for groove or furrow.
1. A complex region of parallel ridges and furrows on a satellite surface, particularly well developed on Ganymede (e.g. Uruk Sulcus, an area of bright, grooved terrain bordering Galileo Regio).
2. A major, rounded depression on the longitudinal mid-line of a brachiopod (Brachiopoda) shell. It usually occurs in the ventral valve and is usually accompanied by a major, rounded, shell elevation (fold) in the other valve.