The inferior frontal gyrus is one of four such gyri in the frontal lobe. These series of convolutions called gyri (singular, gyrus) are perhaps the most distinguishing feature of the external cerebral surface. Between them are grooves of varying depth called sulci (singular, sulcum) or fissures. The frontal lobe is crossed over by three sulci, which divide the frontal lobe into four gyri. The three sulci are the precentral, superior frontal, and inferior frontal sulci and the four gyri are the precentral, superior frontal, middle frontal, and inferior frontal gyri.