definition
Well grounded or justifiable, pertinent.
example
I will believe him as soon as he offers a valid answer.
definition
Acceptable, proper or correct; in accordance with the rules.
example
A valid format for the date is MM/DD/YY.
definition
Related to the current topic, or presented within context, relevant.
definition
Of a formula or system: such that it evaluates to true regardless of the input values.
definition
Of an argument: whose conclusion is always true whenever its premises are true.
example
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.
definition
Effective.
example
He is a priest now: although his ordination was contrary to the law of the church, it was still valid.