invalid

¹ American  

[in-vuh-lid] / ˈɪn və lɪd /

noun

1. an infirm or sickly person.

2. a person who is too sick or weak to take care of their own needs.

   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.

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.

verb (used without object)

Archaic.

1. to become an invalid.

invalid ² American  

[in-val-id] / ɪnˈvæl ɪd /

adjective

1. not valid; not founded in truth, fact, or logic, and hence weak and indefensible; unsound; untenable.

   The entire argument depends on an invalid assumption.

   Synonyms:

   incorrect, inaccurate, false, erroneous, unsubstantiated, unfounded, groundless, baseless

2. deficient in effectiveness; inadequate.

   Self-perception is an invalid method of judging one's own biases.

3. void or without legal force, as a contract.

   Without the grandfather clause, thousands of such warranties would now be invalid. The coupon is invalid in our state.

   Synonyms:

   null and void

4. not accepted or permitted because a required element or the necessary form is lacking; not usable.

   Anything with fewer than five characters is an invalid password, and you’ll get an error message prompting you to pick something more secure.

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invalid ¹ British  

/ ˈɪnvəˌliːd, -lɪd /

noun

1. 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

verb

1. to cause to become an invalid; disable

2. (usually foll by out; often passive) to require (a member of the armed forces) to retire from active service through wounds or illness

invalid ² British  

/ ɪnˈvælɪd, ˌɪnvəˈlɪdɪtɪ /

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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Usage

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

Other Word Forms

• invalidity noun
• invalidly adverb
• invalidness noun

Etymology

Origin of invalid¹

First recorded in 1635–45; from French invalide, from Latin invalidus “weak, feeble, infirm”; See in- ³, valid

Origin of invalid²

First recorded in 1630–40; from Latin invalidus “weak, feeble”; invalid ¹

Example Sentences

Placing an IRA directly in a trust during his lifetime is legally invalid and could trigger significant tax or estate-planning issues.

From MarketWatch • Mar. 31, 2026

District Judge Royce Lamberth's order comes 10 days after he ruled that President Donald Trump's pick to oversee mass layoffs at VOA was unlawfully appointed, rendering the job cuts invalid.

From Barron's • Mar. 17, 2026

Some candidates who submitted petitions by the March 4 deadline failed to qualify because some of their signatures were deemed invalid.

From Los Angeles Times • Mar. 14, 2026

"This was invalid as the permission of the Attorney General had not been obtained at that time," the judgement stated.

From BBC • Mar. 11, 2026

“Maybe they saw the fever rag and thought there was still an invalid in the house.”

From "Fever 1793" by Laurie Halse Anderson

Related Words

• baseless
• false
• inoperative
• irrational
• null
• unfounded
• unreasonable
• unscientific
• unsound
• untrue