coma

1 [koh-muh]
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:
1640–50; < Greek kôma deep sleep

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coma

2 [koh-muh]
noun, plural comae [koh-mee] .
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.
a.
a tuft of silky hairs at the end of a seed.
b.
the leafy crown of a tree; cluster of leaves at the end of a stem.
c.
a terminal cluster of bracts, as in the pineapple.

Origin:
1660–70; < Latin: hair < Greek kómē

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Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
coma1 (ˈkəʊmə)
 
n , 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
 
[C17: from medical Latin, from Greek kōma heavy sleep; related to Greek koitē bed, perhaps to Middle Irish cuma grief]

coma2 (ˈkəʊmə)
 
n , pl -mae
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
 a.  a tuft of hairs attached to the seed coat of some seeds
 b.  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
 
[C17: from Latin: hair of the head, from Greek komē]
 
'comal2
 
adj

Collins English Dictionary - Complete & Unabridged 10th Edition
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Etymonline
Word Origin & History

coma
1646, from Gk. koma (gen. komatos) "deep sleep." Comatose first recorded 1755.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

coma co·ma (kō'mə)
n.
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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American Heritage
Science Dictionary
coma 1   (kō'mə)  Pronunciation Key 
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   (kō'mə)  Pronunciation Key 
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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American Heritage
Cultural Dictionary
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 American Heritage® 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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Example sentences
Yet if not dead, there are many signs that separatism has slumped into a deep
  coma.
Fluid builds up in the lungs and the brain swells, leading to confusion and
  even coma.
Alcohol depresses brain function in dogs and can send them into a coma.
If the tests show brain activity, the patient may be in a coma or vegetative
  state.
Image for coma
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