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invalid1

[in-vuh-lid; British in-vuh-leed]
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noun
  1. an infirm or sickly person.
  2. a person who is too sick or weak to care for himself or herself: My father was an invalid the last ten years of his life.
  3. Archaic. a member of the armed forces disabled for active service.
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adjective
  1. unable to care for oneself due to infirmity or disability: his invalid sister.
  2. of or for invalids: invalid diets.
  3. (of things) in poor or weakened condition: the invalid state of his rocking chair.
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verb (used with object)
  1. to affect with disease; make an invalid: He was invalided for life.
  2. to remove from or classify as not able to perform active service, as an invalid.
  3. British. to remove or evacuate (military personnel) from an active theater of operations because of injury or illness.
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verb (used without object) Archaic.
  1. to become an invalid.
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Origin of invalid1

1635–45; < French invalide < Latin invalidus weak. See in-3, valid

invalid2

[in-val-id]
adjective
  1. not valid; without force or foundation; indefensible.
  2. deficient in substance or cogency; weak.
  3. void or without legal force, as a contract.
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Origin of invalid2

1625–35; < Medieval Latin invalidus, Latin: weak; see invalid1
Related formsin·val·id·ly, adverbin·val·id·ness, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for invalid

invalid1

noun
    1. a person suffering from disablement or chronic ill health
    2. (as modifier)an invalid chair
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adjective
  1. suffering from or disabled by injury, sickness, etc
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verb (tr)
  1. to cause to become an invalid; disable
  2. (usually foll by out; often passive) mainly British to require (a member of the armed forces) to retire from active service through wounds or illness
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Derived Formsinvalidity, noun

Word Origin

C17: from Latin invalidus infirm, from in- 1 + validus strong

usage

It is best to avoid using the term invalid when referring to people with chronic illnesses or disabilities

invalid2

adjective
  1. not valid; having no cogency or legal force
  2. logic (of an argument) having a conclusion that does not follow from the premises: it may be false when the premises are all true; not valid
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Derived Formsinvalidity (ˌɪnvəˈlɪdɪtɪ) or invalidness, nouninvalidly, adverb

Word Origin

C16: from Medieval Latin invalidus without legal force; see invalid 1
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 invalid

adj.1

"not strong, infirm," 1640s, from Latin invalidus "not strong, infirm, weak, feeble," from in- "not" (see in- (1)) + validus "strong" (see valid). Specific meaning "infirm from sickness, disease, or injury" is from 1640s.

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n.

1709, originally of disabled military men, from invalid (adj.1). Invalides is short for French Hôtel des Invalides, home for old and disabled soldiers in the 7th arrondissement of Paris.

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adj.2

"of no legal force," 1630s, from special use of Latin invalidus (see invalid (adj.1)).

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Online Etymology Dictionary, © 2010 Douglas Harper

invalid in Medicine

invalid

(ĭnvə-lĭd)
n.
  1. One who is incapacitated by a chronic illness or disability.
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adj.
  1. Incapacitated by illness or injury.
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.