VIM concept: verification and validation, one letter and one question apart

Verification and validation get used interchangeably in quality systems, and the VIM's pair of definitions is the cleanest cure. Verification (2.44): objective evidence that an item fulfils SPECIFIED requirements. Validation (2.45): verification where the requirements are shown to be ADEQUATE FOR AN INTENDED USE.

The difference is the question being answered. Verification asks 'does it meet the spec?' — the balance holds ±0.1 mg, the method achieves its claimed repeatability. Validation asks the prior question: 'is that spec the right one for this use?' A method can verify beautifully against requirements that are wrong for the job — the classic audit finding hiding behind a wall of passing checks.

NIST's GLP 14 in the library operationalizes validation for measurement methods: performance characteristics to establish, experiments that establish them, and the documentation that makes 'fit for intended use' a demonstrated claim rather than a hope. The dictionary carries both VIM entries, one click apart, for the next time a procedure conflates them.