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ISO 31 (Quantities and units, International Organization for Standardization, 1992) is a deprecated international standard for the use of physical quantities and units of measurement, and formulas involving them, in scientific and educational documents. It is superseded by ISO/IEC 80000.
The standard comes in 14 parts:
A second international standard on quantities and units was IEC 60027. The ISO 31 and IEC 60027 Standards were revised by the two standardization organizations in collaboration (, ) to integrate both standards into a joint standard ISO/IEC 80000 - Quantities and Units in which the quantities and equations used with SI are to be referred as the International System of Quantities (ISQ). ISO/IEC 80000 supersedes both ISO 31 and part of IEC 60027.
ISO 31-0 introduced several new words into the English language that are direct spelling-calques from the French. The intention was that these words be used in scientific papers for the sake of convenience and clarity.
||a quantity divided by its associated mass
||[volumic] <quantity> density
||a quantity divided by its associated volume
||surface <quantity> density
||a quantity divided by its associated area
||linear <quantity> density
||a quantity divided by its associated length
Related national standards
- Canada: CAN/CSA-Z234-1-89 Canadian Metric Practice Guide (covers some aspects of ISO 31-0, but is not a comprehensive list of physical quantities comparable to ISO 31)
- United States: There are several national SI guidance documents, such as NIST SP 811, NIST SP 330, NIST SP 814, IEEE/ASTM SI 10, SAE J916. These cover many aspects of the ISO 31-0 standard, but lack the comprehensive list of quantities and units defined in the remaining parts of ISO 31.
- SI - the international system of units
- BIPM - publishes freely available information on SI units , which overlaps with some of the material covered in ISO 31-0
- IUPAP - much of the material in ISO 31 comes originally from Document IUPAP-25 of the Commission for Symbols, Units and Nomenclature (SUN Commission)  of the International Union of Pure and Applied Physics
- IUPAC - some of the material in ISO 31 originates from the Interdivisional Committee on Terminology, Nomenclature and Symbols  of the International Union of Pure and Applied Chemistry
- Quantities, Units and Symbols in Physical Chemistry - this IUPAC "Green Book" covers many ISO 31 definitions
- IEC 60027 Letter symbols to be used in electrical technology
- ISO 1000 SI Units and Recommendations for the use of their multiples and of certain other units (bundled with ISO 31 as the ISO Standards Handbook - Quantities and units)