# invalid

/ˈɪnvəɫəd/ (US)

Source: https://englishreference.com/word/invalid
Updated: 2026-06-20

## Senses

### 1. not legally or logically correct

adjective · CEFR B1

not true, correct, or acceptable according to the rules.

For teachers: lacking legal force or logical validity; null and void.

- The website said my password was invalid because I used the wrong characters.
- The contract was declared invalid by the court because one of the signatures had been forged.

Usage: The stress is on the second syllable: in-VAL-id.

### 3. to release from duty due to illness

verb · CEFR C1 · British English · Formal

to officially allow someone to leave the army or a job because they are too sick to work.

For teachers: to remove someone from active duty, particularly in a military context, due to injury or chronic ill health.

- The soldier was invalided out of the army after losing his sight in the war.
- He was eventually invalided home after contracting a tropical fever that left him unable to perform his duties.

Usage: Usually appears in the passive voice as 'to be invalided out'.

Teaching tip: This is a specialized term mostly found in historical or military literature.

## Examples

- Your password is invalid, so please try again.
- The judge ruled that the contract was invalid because one of the signatures had been forged.
- The entire scientific study was deemed invalid after an independent audit discovered that the researchers had manipulated the raw data to support their initial hypothesis.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.