International Vocabulary of Metrology

The International Vocabulary of Metrology (VIM) is a harmonized set of definitions for terms used in metrology, the science of measurement. It is intended to promote a common language among scientists, engineers, and regulators, reducing ambiguity in international trade, research, and legal requirements. The VIM covers fundamental concepts such as quantity, unit, measurement, and measurement error, as well as more specialized terms like calibration and measurement uncertainty.¹ The document is officially designated as JCGM 200, and its full title is International Vocabulary of Metrology – Basic and General Concepts and Associated Terms.²

The first edition of the VIM was published in 1984, following a collaborative effort by the BIPM, the International Electrotechnical Commission (IEC), the International Organization for Standardization (ISO), and the International Organization of Legal Metrology (OIML). A second edition appeared in 1993, and the third edition, which is currently in use, was published in 2008.³ The third edition introduced significant changes, including a more rigorous treatment of uncertainty and a clearer distinction between metrological traceability and measurement traceability. The VIM is maintained by the JCGM, which also publishes the Guide to the Expression of Uncertainty in Measurement (GUM).

The VIM is organized into thematic sections, each addressing a cluster of related concepts. The main sections cover quantities and units, measurement results, measuring instruments, and properties of measuring instruments. Each term is defined with a concise, authoritative statement, and many entries include notes that clarify usage or provide examples. The definitions are intended to be independent of any particular field, making the VIM applicable across physics, chemistry, biology, and engineering. The document also includes an extensive index and a bibliography of related standards.

While the VIM is widely used in calibration laboratories, its influence extends to legal metrology, where it informs regulations on weights and measures. The VIM also plays a role in education, serving as a basis for university courses in measurement science. A lesser-known fact is that the VIM is available in multiple languages, including French and English, with translations into other languages coordinated by national metrology institutes. The third edition was notably revised to align with the International System of Units (SI) and to incorporate concepts from the GUM, ensuring consistency between the two documents.⁴

Metrology

The science of measurement, embracing both experimental and theoretical determinations at any level of uncertainty.

Measurement uncertainty

A parameter that characterizes the dispersion of values that could reasonably be attributed to a measurand.

Traceability

The property of a measurement result whereby it can be related to a stated reference through a documented unbroken chain of calibrations.