cor·​tex | \ˈkȯr-ˌteks \
plural cortices\ ˈkȯr-​tə-​ˌsēz \ 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

The latest is called cortical spreading depression, which refers to a spontaneous electrical wave that travels through the brain’s cortex. Tony Dajer, Discover Magazine, "Vertigo, Panic and Trouble Breathing: What's Going On Here?," 19 Oct. 2018 One of the regions in that network is the frontopolar cortex, which, according to Vago, evidence suggests is the most highly evolved part of the brain and is thought to be responsible for supporting meta-awareness. Carolyn L. Todd, SELF, "What Meditation Can—and Can’t—Do for Your Health," 11 Sep. 2018 Activity in our brains is malleable, allowing higher-order circuits in the cortex to modify the more primitive fear and reward systems to produce different behavioral outcomes. Leslie Henderson, Scientific American, "Why Our Brains See the World as "Us" versus "Them"," 22 June 2018 However, in a young child who becomes blind, as with Helen Keller, this same cortex can be repurposed for entirely distinct functions, like language processing. New York Times, "My Patient’s Smile," 16 May 2018 With Neuropixels, scientists have realized these signals are more common in the cortex than previously thought. Daniela Hernandez, WSJ, "The Quest to Decode the Brain," 15 June 2018 Independently, parrots have evolved an enlarged area that connects the cortex and the cerebellum, similar to primates. Brigit Katz, Smithsonian, "Unique Brain Circuitry Might Explain Why Parrots Are So Smart," 7 July 2018 Two thirds of the clusters detected were traveling waves moving from the rear to the front of the cortex. Simon Makin, Scientific American, "“Traveling” Brain Waves May Be Critical for Cognition," 28 June 2018 Subjects showed marked activation in the parts of the brain associated with pleasure and feeling good, in particular the orbitofrontal cortex. Linda Rodriguez Mcrobbie,, "How ice cream made America," 30 June 2018

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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Statistics for cortex

Last Updated

15 Nov 2018

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The first known use of cortex was in 1677

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English Language Learners Definition of cortex

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


cor·​tex | \ˈkȯr-ˌteks \
plural cortices\ ˈkȯrt-​ə-​ˌsēz \ 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

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a private place of worship

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