The human cortex occupies most of the brain as seen in the illustration. Let's compare the definitions of cortex with other fields of science.
The cortex applies to many fields of science.
Cortex (archaeology), the outer layer of rock formed on the exterior of raw materials by chemical and mechanical weathering processes
Cortex (botany), the outer portion of the stem or root of a plant
Cortex (anatomy), the outermost or superficial layer of an organ
Cortex (hair), the middle layer of a strand of hair
Organs
Cell cortex, the region proximal to the cell surface, i.e. directly underneath the cell membrane
the Renal cortex, the outer portion of the kidney
the Adrenal cortex, the portion of the Adrenal gland responsible for the production of cortisol and aldosterone
The brain
the Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the forebrain
the Motor cortex, the regions of the cerebral cortex involved in voluntary motor functions
the Prefrontal cortex, the anterior part of the frontal lobes of the brain
the Visual cortex, regions of the cerebral cortex involved in visual functions
the Cerebellar cortex, the outer layer of the vertebrate cerebellum
Index to the Brain Cortex
http://humanoidolabs.blogspot.tw/2013/11/brain-cortex-index-part-16.html