Title: SI
Long Title: IUPAC Gold Book - SI
DOI: 10.1351/goldbook.S05653
Status: current

Definition
Système International d'Unités, the international system of units established in 1960 and based on seven base units for the quantities: length, time, mass, electric current, thermodynamic temperature, amount of substance and luminous intensity.

Related Terms
- Système International d'Unités: https://goldbook.iupac.org/terms/view/S06238
- amount of substance: https://goldbook.iupac.org/terms/view/A00297
- electric current: https://goldbook.iupac.org/terms/view/E01927
- luminous intensity: https://goldbook.iupac.org/terms/view/L03647
- thermodynamic temperature: https://goldbook.iupac.org/terms/view/T06321

Source
- Green Book, 2nd ed., p. 69 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)

Related Reference
- PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 995 (https://doi.org/10.1351/pac199668040957)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/S05653/html
- json: https://goldbook.iupac.org/terms/view/S05653/json
- xml: https://goldbook.iupac.org/terms/view/S05653/xml

Citation: Citation: 'SI' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.S05653
License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms.
Collection: If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .
Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.
Accessed: 2026-06-30T21:33:10+00:00