valid

Valid is an adjective describing something that is legally, logically, or generally acceptable, sound, or well-founded according to recognized rules or standards. It can refer to arguments, claims, documents, credentials, or reasons that meet established requirements or truth conditions. In everyday use, a valid reason or ticket is one that is acceptable or legitimate.

Etymology and usage notes: The word derives from the Latin validus meaning strong or effective, from valere “to be strong.” In English, valid often contrasts with invalid or void, signaling that something meets the relevant criteria rather than being null or compromised.

Logical validity: In logic, an argument is valid if its conclusion follows necessarily from its premises; if the premises are true, the conclusion cannot be false. Validity concerns form rather than content. A valid argument can have false premises and a false conclusion, but a sound argument is both valid and with true premises.

Legal and formal validity: In law and formal contexts, validity means that something complies with applicable rules, statutes, or contractual terms. A contract, will, license, or marriage can be described as valid if it meets required formalities and remains enforceable. Validity can be challenged on grounds such as fraud, coercion, or lack of capacity.

Data and systems validity: In computing and information management, data validity refers to data that adheres to defined formats and rules, ensuring accuracy and usefulness. Validation processes check inputs, types, ranges, and consistency. Digital certificates have a validity period, after which they may be considered expired or invalid.

Distinctions: Validity is often distinguished from truth and from correctness of details; it concerns adherence to rules and logical coherence, not every factual claim. Invalid, void, or unsound are common opposites depending on context.