Definition of "valid" in English

adjective

1. Well-grounded or justifiable, pertinent.

   • I will believe him as soon as he offers a valid answer.

2. Acceptable, proper or correct; in accordance with the rules.

   • A valid format for the date is DD/MM/YY.
   • Do not drive without a valid license.

3. Related to the current topic, or presented within context, relevant.

4. (logic) Of a formula or system: such that it evaluates to true regardless of the input values.

5. (logic) Of an argument: whose conclusion is always true whenever its premises are true.

   • An argument is valid if and only if the set consisting of both (1) all of its premises and (2) the contradictory of its conclusion is inconsistent.

6. (Christianity, theology) Genuine - as distinguished from efficient or regular - sacrament.