The international standard ISO 80000, or IEC 80000, is a style guide for the use of physical quantities and units of measurement, and formulas involving them, in scientific and educational documents worldwide. In most countries, the notations used in mathematics and science textbooks at schools and universities follow closely the guidelines in this standard.
The standard is jointly issued and maintained by the International Organization for Standardization (ISO) the International Electrotechnical Commission (IEC). The ISO/IEC 80000 family of standards was completed with the publication of Part 1 in November 2009. The introduction to Part 1 states "The system of quantities, including the relations among the quantities used as the basis of the units of the SI, is named the International System of Quantities, denoted ISQ, in all languages."
The Standard has 14 parts:
|ISO 80000-1||General||ISO 31-0, IEC 60027-1 and IEC 60027-3|
|ISO 80000-2||Mathematical signs and symbols to be used in the natural sciences and technology||ISO 31-11, IEC 60027-1|
|ISO 80000-3||Space and time||ISO 31-1 and ISO 31-2|
|ISO 80000-4||Mechanics||ISO 31-3|
|ISO 80000-5||Thermodynamics||ISO 31-4|
|IEC 80000-6||Electromagnetism||ISO 31-5, IEC 60027-1|
|ISO 80000-7||Light||ISO 31-6|
|ISO 80000-8||Acoustics||ISO 31-7|
|ISO 80000-9||Physical chemistry and molecular physics||ISO 31-8|
|ISO 80000-10||Atomic and nuclear physics||ISO 31-9 and ISO 31-10|
|ISO 80000-11||Characteristic numbers||ISO 31-12|
|ISO 80000-12||Solid state physics||ISO 31-13|
|IEC 80000-13||Information science and technology||subclauses 3.8 and 3.9 of IEC 60027-2:2005 and IEC 60027-3|
|IEC 80000-14||Telebiometrics related to human physiology||IEC 60027-7|
IEC TC 25 
- the set of mathematical signs and symbols
- the SI
- the symbols for chemical elements
- the way of writing notes for music
The first three systems will be given in ISO/IEC 80000.
Binary prefixes 
A 1999 addendum to IEC 60027-2 on binary prefixes has resulted in some public interest in the standard and is still being widely discussed in the computer community, as it attempts to finally settle the confusion about whether, e.g., a kilobit corresponds to 1000 bits or 1024 bits.
The harmonized IEC 80000-13:2008 standard cancels and replaces subclauses 3.8 and 3.9 of IEC 60027-2:2005 (those defining Prefixes for binary multiples). The only significant change is the addition of explicit definitions for some quantities.
See also 
- International Vocabulary of Metrology
- International System of Units
- BIPM — publishes freely available information on SI units
- NIST — official U.S. representative for SI; publishes freely available guide to use of SI
- IEC: SI Zone: The present situation in the IEC. Consulted 2009-07-28.
- BIPM SI Brochure
- ISO TC12 standards — Quantities, units, symbols, conversion factors
- NIST Special Publication 330 — The International System of Units
- NIST Special Publication 811 — Guide for the Use of the International System of Units