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[koh-muh] /ˈkoʊ mə/
noun, plural comas.
a state of prolonged unconsciousness, including a lack of response to stimuli, from which it is impossible to rouse a person.
Origin of coma1
First recorded in 1640-50, coma is from the Greek word kôma deep sleep


[koh-muh] /ˈkoʊ mə/
noun, plural comae
[koh-mee] /ˈkoʊ mi/ (Show IPA)
Astronomy. the nebulous envelope around the nucleus of a comet.
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.
  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.
1660-70; < Latin: hair < Greek kómē Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for coma


noun (pl) -mas
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
Word Origin
C17: from medical Latin, from Greek kōma heavy sleep; related to Greek koitē bed, perhaps to Middle Irish cuma grief


noun (pl) -mae (-miː)
(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
  1. a tuft of hairs attached to the seed coat of some seeds
  2. the terminal crown of leaves of palms and moss stems
(optics) a type of lens defect characterized by the formation of a diffuse pear-shaped image from a point object
Derived Forms
comal, 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
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Word Origin and History for coma

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


"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).

Online Etymology Dictionary, © 2010 Douglas Harper
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coma in Medicine

coma co·ma (kō'mə)
A state of profound unconsciousness in which an individual is incapable of sensing or responding to external stimuli.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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coma in Science
coma 1
Plural comas
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.
coma 2
Plural comae (kō'mē)
  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.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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coma in Culture
coma [(koh-muh)]

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.

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