validity

Everyday

1. Validity is how true, fair or correct something is, for example an argument or a test. tree →
2. (law) Validity is whether a document, ticket or rule is official and still accepted, for example a passport's validity. tree →

In the lessons

In maths and logic it means an argument follows correctly from its premises. In science it means a test really measures what it should (a fair test). In everyday life it is about tickets, passports and cards that have not expired. Phrases: the validity of, check the validity, period of validity.

Examples

• The scientist questioned the validity of the results. tree →
• Check the validity of your passport before you travel. tree →
• A fair test makes your experiment more valid; that is its validity. tree →
• The ticket's validity ends at midnight. tree →
• The judge looked at the validity of the will. tree →
• The teacher asked us to judge the validity of each argument. tree →

Note

Mostly uncountable. Adjective: valid; opposite: invalid. Trap in logic: an argument can be valid (the steps follow) even if a premise is false.