cortex

noun

cor·​tex ˈkȯr-ˌteks 

plural cortices ˈkȯr-tə-ˌsēz  also cortexes

1

a(1)

: the outer or superficial part of an organ or bodily structure (such as the kidney, adrenal gland, or cerebellum or a bone)

especially : cerebral cortex

(2)

: the proteinaceous usually pigmented layer of a hair below the cuticle

b

: the outer part of some organisms (such as paramecia)

2

: a plant bark or rind (such as cinchona) used medicinally

3

a

: the typically parenchymatous layer of tissue external to the vascular tissue and internal to the corky or epidermal tissues of a green plant

broadly : all tissues external to the xylem

b

: an outer or investing layer of various algae, lichens, or fungi

Examples of cortex in a Sentence

Recent Examples on the Web

These electrodes record neural firing patterns in the motor cortex, where the brain controls the lips, tongue and larynx. —Kurt Knutsson, FOXNews.com, 27 Nov. 2025

This formula features a ferment blend to support the scalp and a trio of African oils, baobab, moringa, and black seed, that slip past raised cuticles to replenish the inner cortex, improving elasticity and reducing breakage. —Jailynn Taylor, Allure, 25 Nov. 2025

The volunteers will each have one electrode array implanted in the motor cortex region that controls the lips, tongue and larynx. —New Atlas, 21 Nov. 2025

The limbic system has two neighboring regions, the hippocampus and the entorhinal cortex, both of which are implicated in spatial cognition. —Literary Hub, 14 Nov. 2025

Word History

Etymology

Latin cortic-, cortex bark — more at cuirass

First Known Use

circa 1676, in the meaning defined at sense 1a(1)

Phrases Containing cortex

• cerebral cortex
• piriform cortex
• prefrontal cortex
• pyriform cortex
• visual cortex

Rhymes for cortex

• vortex
• neocortex

Kids Definition

cortex

noun

cor·​tex ˈkȯr-ˌteks 

plural cortices ˈkȯrt-ə-ˌsēz  or cortexes

1

: an outer or surrounding layer of an organ or body part

the cortex of the kidney

especially : the outer layer of gray matter of the cerebrum

2

: the layer of tissue outside the xylem and phloem and inside the corky or epidermal tissues of a vascular plant

also : all tissues external to the xylem

Medical Definition

cortex

noun

cor·​tex ˈkȯr-ˌteks 

plural cortices ˈkȯrt-ə-ˌsēz  also cortexes

1

a

: the outer or superficial part of an organ or body structure (as the kidney, adrenal gland, or a hair)

especially : cerebral cortex

b

: the outer part of some organisms (as paramecia)

2

a

: a plant bark or rind (as cinchona) used medicinally

b

: the peel of any of several fruits

—used especially in the writing of medical prescriptions