cor·​tex | \ ˈkȯr-ˌteks How to pronounce cortex (audio) \
plural cortices\ ˈkȯr-​tə-​ˌsēz How to pronounce cortex (audio) \ or cortexes

Definition of cortex

1a(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
3a : 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 When comparing responses, the team at Eotvos Lorand University, Budapest, also found distinct activity patterns in the dogs' primary auditory cortex. People Staff,, 6 Jan. 2022 Sure enough, the brain scans showed different activity patterns in the primary auditory cortex when nonsense words were spoken than when natural speech occurred. Sandee Lamotte, CNN, 6 Jan. 2022 These were stuck into four sections of their brains: three regions of the cortex and the thalamus. Max G. Levy, Wired, 11 May 2021 Other researchers using brain imaging data from the U.K. recently discovered evidence of tissue damage, a thinner cortex, and loss of gray matter in people who had tested positive for the virus. Sharon Guynup, Science, 29 Dec. 2021 The higher brain — especially the pre-frontal cortex — is responsible for executive functions. Dr. Denise Trudeau-poskas, Forbes, 7 Dec. 2021 There were multiple lesions, mostly in the frontal cortex of his brain. New York Times, 16 Dec. 2021 The treatment opens up the cuticle, allowing the amino acids to enter the cortex of the hair. Margaux Lushing, Forbes, 1 Nov. 2021 That suggests other higher-up brain regions, such as the frontal cortex, are telling the visual area to pay attention to faces, which quickly leads to the maturation of the region dedicated to detecting them. Dana G. Smith, Scientific American, 15 Nov. 2021

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'cortex.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of cortex

1677, in the meaning defined at sense 1a(1)

History and Etymology for cortex

Latin cortic-, cortex bark — more at cuirass

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Last Updated

17 Jan 2022

Cite this Entry

“Cortex.” Dictionary, Merriam-Webster, Accessed 24 Jan. 2022.

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English Language Learners Definition of cortex

: the outer layer of an organ in the body and especially of the brain


cor·​tex | \ ˈkȯr-ˌteks How to pronounce cortex (audio) \
plural cortices\ ˈkȯrt-​ə-​ˌsēz How to pronounce cortex (audio) \ or cortexes

Medical Definition of cortex

1a : 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)
2a : 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

More from Merriam-Webster on cortex

Nglish: Translation of cortex for Spanish Speakers

Britannica English: Translation of cortex for Arabic Speakers Encyclopedia article about cortex


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