What is the name for a furrow or groove that separates the folds of the brain?

The term that describes a furrow or groove separating the folds of the brain is "sulcus." Sulci (plural for sulcus) are essential features of the brain’s anatomy, as they increase the surface area available for neuronal connections, allowing the brain to perform more complex functions.

In the context of brain structure, a sulcus is shallow and smaller than a fissure, which is a deeper groove. The gyrus refers to the raised folds themselves, while cleavage is not a term used in neuroanatomy in this context. Understanding these definitions clarifies why "sulcus" is the correct term to denote the grooves that separate the brain's gyri.