Gyrus is a term used in anatomy and neurology to describe a rounded ridge or swelling on the surface of an organ, particularly referring to the brain. In more specific terms, it can refer to one of several distinct regions within the cerebral cortex that are characterized by their unique patterns of folding and organization. These gyri and sulci (folds) give the outer surface of the brain its characteristic appearance and help to increase the overall surface area available for neural processing.