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noun, plural co·mas.
  1. a state of prolonged unconsciousness, including a lack of response to stimuli, from which it is impossible to rouse a person.
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Origin of coma1

First recorded in 1640–50, coma is from the Greek word kôma deep sleep


noun, plural co·mae [koh-mee] /ˈkoʊ mi/.
  1. Astronomy. the nebulous envelope around the nucleus of a comet.
  2. Optics. a monochromatic aberration of a lens or other optical system in which the image from a point source cannot be brought into focus, the image of a point having the shape of a comet.
  3. Botany.
    1. a tuft of silky hairs at the end of a seed.
    2. the leafy crown of a tree; cluster of leaves at the end of a stem.
    3. a terminal cluster of bracts, as in the pineapple.
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Origin of coma2

1660–70; < Latin: hair < Greek kómē
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for coma


noun plural -mas
  1. a state of unconsciousness from which a person cannot be aroused, caused by injury to the head, rupture of cerebral blood vessels, narcotics, poisons, etc
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Word Origin

C17: from medical Latin, from Greek kōma heavy sleep; related to Greek koitē bed, perhaps to Middle Irish cuma grief


noun plural -mae (-miː)
  1. astronomy the luminous cloud surrounding the frozen solid nucleus in the head of a comet, formed by vaporization of part of the nucleus when the comet is close to the sun
  2. botany
    1. a tuft of hairs attached to the seed coat of some seeds
    2. the terminal crown of leaves of palms and moss stems
  3. optics a type of lens defect characterized by the formation of a diffuse pear-shaped image from a point object
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Derived Formscomal, adjective

Word Origin

C17: from Latin: hair of the head, from Greek komē
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for coma


state of prolonged unconsciousness, 1640s, from Latinized form of Greek koma (genitive komatos) "deep sleep," of uncertain origin.

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"head of a comet," 1765, from Latin coma, from Greek kome "hair of the head," of unknown origin. Earlier in English as a botanical term for a tuft of hairs (1660s).

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Online Etymology Dictionary, © 2010 Douglas Harper

coma in Medicine


  1. A state of profound unconsciousness in which an individual is incapable of sensing or responding to external stimuli.
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

coma in Science


Plural comas
  1. A state of deep unconsciousness, usually resulting from brain trauma or metabolic disease, in which an individual is incapable of sensing or responding to external stimuli.
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Plural comae ()
  1. Astronomy The brightly shining cloud of gas that encircles the nucleus and makes up the major portion of the head of a comet near the Sun. As a comet moves along its orbit away from the Sun, the gas and dust of the coma dissipate, leaving only the nucleus. A coma can have a diameter of up to 100,000 km (62,000 mi.). See more at comet.
  2. Physics A diffuse, comet-shaped image of a point source of light or radiation caused by aberration in a lens or mirror. The image appears progressively elongated with distance from the center of the field of view.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

coma in Culture



An abnormal state of deep unconsciousness. A coma may occur as the result of trauma to the head, disease (such as meningitis, stroke, or diabetes mellitus), or poisoning.

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The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.