invalid

UK: noun: /ˈɪnvəlɪd/, adjective: /ɪnˈvælɪd/

US: /ˈɪnvəlɪd/

US: (in′və lid, Brit. in′və lēd′ for 1; in val′id for 2)

WordReference Random House Learner's Dictionary of American English © 2025

in•va•lid¹ /ˈɪnvəlɪd/   n. [countable]

1. an unhealthy person, esp. one who is too sick or weak to care for himself or herself.

adj. 

2. unable to care for oneself, as through ill health.
3. of or for invalids.

v. [~ + object]

4. to make (someone) an invalid.
5. Military [Chiefly Brit.] to evacuate (military personnel) from an area of fighting because of injury or illness.

in•val•id² /ɪnˈvælɪd/   adj. 

1. not valid; without force or a firm foundation;
   that cannot be defended;
   weak in logic:
   an invalid conclusion.
2. empty or without legal force:
   The contract was declared invalid.

in•va•lid•i•ty /ˌɪnvəˈlɪdɪti/  n. [uncountable]

WordReference Random House Unabridged Dictionary of American English © 2025

in•va•lid¹  (in′və lid; Brit. in′və lēd′), n. 

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.

adj. 

4. unable to care for oneself due to infirmity or disability:
   his invalid sister.
5. of or for invalids:
   invalid diets.
6. (of things) in poor or weakened condition:
   the invalid state of his rocking chair.

v.t. 

7. to affect with disease;
   make an invalid:
   He was invalided for life.
8. to remove from or classify as not able to perform active service, as an invalid.
9. Military [Brit.] to remove or evacuate (military personnel) from an active theater of operations because of injury or illness.

v.i. Archaic. 

10. to become an invalid.

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

in•val•id²  (in val′id), adj. 

1. not valid;
   without force or foundation;
   indefensible.
2. deficient in substance or cogency;
   weak.
3. void or without legal force, as a contract.

• Medieval Latin invalidus, Latin: weak; see invalid¹
• 1625–35

in•val′id•ly, adv. 
in•val′id•ness, n. 

Collins Concise English Dictionary © HarperCollins Publishers::

invalid / ˈɪnvəlɪd/ noun

1. a person with disablement or chronic ill health
2. (as modifier): an invalid chair

adjective

1. incapacitated or disabled by injury, sickness, etc

verb (transitive)

1. to cause to become an invalid; disable
2. (usually followed by out; often passive) to require (a member of the armed forces) to retire from active service through wounds or illness

Etymology: 17th Century: from Latin invalidus infirm, from in-¹ + validus strong

ˌinvaˈlidity noun

invalid / ɪnˈvælɪd/ adjective

not valid; having no cogency or legal force

(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

Etymology: 16th Century: from Medieval Latin invalidus without legal force; see invalid¹

invalidity / ˌɪnvəˈlɪdɪtɪ/, inˈvalidness noun

inˈvalidly adverb