valid: Meaning and Definition of

val•id

1. sound; just; well-founded: a valid reason.
2. producing the desired result; effective: a valid antidote for gloom.
3. having force, weight, or cogency; authoritative.
4. legally sound, effective, or binding; having legal force: a valid contract.
5. (of an argument) so constructed that if the premises are jointly asserted, the conclusion cannot be denied without contradiction.
6. robust; well; healthy.