Sulcus (morphology)
In biological morphology and anatomy, a sulcus (pl. sulci) is a furrow or fissure (Latin: fissura; pl. fissurae). It may be a groove, natural division, deep furrow, elongated cleft, or tear in the surface of a limb or an organ, most notably on the surface of the brain, but also in the lungs, certain muscles (including the heart), as well as in bones and elsewhere.