ISO 31

ISO 31 (Quantities and units, International Organization for Standardization, 1992) is a superseded international standard concerning physical quantities, units of measurement, their interrelationships and their presentation.^[1] It was revised and replaced by ISO/IEC 80000.

Parts

The standard comes in 14 parts:

• ISO 31-0: General principles (replaced by ISO/IEC 80000-1:2009)
• ISO 31-1: Space and time (replaced by ISO/IEC 80000-3:2007)
• ISO 31-2: Periodic and related phenomena (replaced by ISO/IEC 80000-3:2007)
• ISO 31-3: Mechanics (replaced by ISO/IEC 80000-4:2006)
• ISO 31-4: Heat (replaced by ISO/IEC 80000-5)
• ISO 31-5: Electricity and magnetism (replaced by ISO/IEC 80000-6)
• ISO 31-6: Light and related electromagnetic radiations (replaced by ISO/IEC 80000-7)
• ISO 31-7: Acoustics (replaced by ISO/IEC 80000-8:2007)
• ISO 31-8: Physical chemistry and molecular physics (replaced by ISO/IEC 80000-9)
• ISO 31-9: Atomic and nuclear physics (replaced by ISO/IEC 80000-10)
• ISO 31-10: Nuclear reactions and ionizing radiations (replaced by ISO/IEC 80000-10)
• ISO 31-11: Mathematical signs and symbols for use in the physical sciences and technology (replaced by ISO 80000-2:2009)
• ISO 31-12: Characteristic numbers (replaced by ISO/IEC 80000-11)
• ISO 31-13: Solid state physics (replaced by ISO/IEC 80000-12)

A second international standard on quantities and units was IEC 60027.^[2] 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.

Coined words

ISO 31-0 introduced several new words into the English language that are direct spelling-calques from the French.^[3] Some of these words have been used in scientific literature.^[4][5][6][7]

New phrase	Existing phrase	Technical meaning
massic <quantity>	specific <quantity>	a quantity divided by its associated mass
volumic <quantity>	[volumic] <quantity> density	a quantity divided by its associated volume
areic <quantity>	surface <quantity> density	a quantity divided by its associated area
lineic <quantity>	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.

See also

• 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)