the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum
"The cerebral cortex consists of a thick layer of unmyelinated neurons that processes sensory information and controls voluntary movement."
the tissue forming the outer layer of an organ or structure in plant or animal
"The cortex is a thick, spongy layer that forms the outer part of many plant roots and stems."
the tissue that surrounds the lens nucleus
"The cortex is the soft, flexible layer of tissue that immediately surrounds the hard nucleus in a young cataractous lens."
The outer layer of an internal organ or body structure, such as the kidney or the brain.
"The surgeon examined the cortex of the patient's damaged kidney to assess tissue viability."
In plain English: The cortex is the outer layer of your brain where thinking and memory happen.
"The dog's behavior was so erratic that he rushed to the animal hospital for an immediate check on his brain cortex."
Usage: Use "cortex" specifically for the outer layer of organs like the brain or kidneys; avoid using it to describe any skin-like surface on other objects. Do not confuse this biological term with "crust," which refers to hard outer shells of planets, eggs, or baked goods.
The word cortex comes from the Latin term cortex, which originally meant "cork" or "bark." It entered English with this same meaning before later being applied to other hard outer layers.