In neuroanatomy, a sulcus (pl. sulci) is a depression or fissure in the surface of the brain.
It surrounds the gyri, creating the characteristic appearance of the brain in humans and other large mammals.
Large furrows (sulci) that divide the brain into lobes are often called fissures. The large furrow that divide the two hemispheres - the interhemispheric fissure - is very rarely called a "sulcus".
The sulcal pattern varies between human individuals, and the most elaborate overview on this variation is probably an atlas by Ono, Kubick and Abernathey: Atlas of the Cerebral Sulci.
Some of the larger sulci are, however, seen across individuals - and even species - so it is possible to establish a nomenclature.
Gyrification across species
The variation in the amount of fissures in the brain ("gyrification") between species is more related to the overall size of the animal rather than the encephalization. That is, large animals have many sulci:
"[L]arge rodents such as beavers (40 pounds) and capybaras (150 pounds) have many more sulci than smaller rodents such as rats and mice - but also more fissures than smaller monkeys".