Validation

The process of demonstrating that the system under consideration meets in all respects the specification of that system.
SOURCE: FIPS 201

Confirmation (through the provision of strong, sound, objective evidence) that requirements for a specific intended use or application have been fulfilled (e.g., a trustworthy credential has been presented, or data or information has been formatted in accordance with a defined set of rules, or a specific process has demonstrated that an entity under consideration meets, in all respects, its defined attributes or requirements).
SOURCE: CNSSI-4009