We are pleased to present the 9th edition of the SI Brochure (2019), which defines and presents the Système International d'Unités, the SI (known in English as the International System of Units).

Complete brochure (French and English) Concise summary Text in English Text in French Appendix 1: Decisions of the CGPM and the CIPM Appendix 2: Practical realization of the definition of some important units Appendix 3: Units for photochemical and photobiological quantities Appendix 4: Historical notes on the development of the SI and its base units

Detailed information for translators and editors on changes to versions of the text made since May 2019 are available on request to the BIPM Webmaster .

NOTE: This work is licensed under a Creative Commons Attribution 4.0 International License.

Previous editions of the SI Brochure

	8th edition (2006) (French and English) and Supplement 2014: updates to the 8th edition
	7th edition (1998) (French and English)
	6th edition (1991) (French and English)
	5th edition (1985) (French and English)
	4th edition (1981) (French only)
	3rd edition (1977) (French only)
	2nd edition (1973) (French only)
	1st edition (1970) (French only)