Sulcus (pl. sulci) is a Latin word :

• used in Latin to refer to a groove, furrow or trench.
• used in planetary geology to refer to subparallel grooves and ditches formed by geological processes. See Sulcus (geology)
• used in medicine to refer to grooves, crevices, and furrows. e.g., superior pulmonary sulcus See Sulcus (medicine)