invalid

Everyday

1. (adjective) Not legally or officially acceptable, as in an invalid ticket. tree →
2. (adjective) Not correct or not based on good reasons, as in an invalid argument or invalid input. tree →
3. (noun, old and can be offensive) A person who is ill or disabled for a long time and needs care. tree →

In the lessons

In everyday life: invalid tickets, passwords or passports are not accepted. In maths and computing: «invalid input» means the computer cannot use what you typed; an invalid answer does not fit the rules. In old stories: an invalid lies in bed. Today «invalid» for a person is considered old-fashioned or hurtful.

Examples

• This ticket is invalid — it's for yesterday's show. tree →
• The password is invalid, try again. tree →
• Your argument is invalid because you skipped a step. tree →
• A cheque without a signature is invalid. tree →
• Her passport was invalid, so she couldn't fly. tree →
• In the old story, the invalid was cared for by his sister. tree →
• It was warranted harmless to infants and invalids, so he felt quite safe. tree →

Note

Two words with different stress: in-VAL-id (not valid) and IN-va-lid (a sick person). Opposite: valid. Verb: invalidate. Use «disabled person» or «person who is ill», not «an invalid».