valid

adjective6

1. •
   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.
2. •
   Genuine - as distinguished from efficient or regular - sacrament.
3. •
   Well-grounded or justifiable, pertinent.

   • I will believe him as soon as he offers a valid answer.
4. •
   Of a formula or system: such that it evaluates to true regardless of the input values.
5. •
   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. •
   Related to the current topic, or presented within context, relevant.