The National Institute of Standards and Technology (NIST) has issued a new American version of the English language SI Brochure, the eighth edition of the international standard reference guide to the modern metric system, the International System of Units (known as SI from the French "Le Systeme International d'Unites"). NIST is the U.S. technical representative to the International Bureau of Weights and Measures that defines the SI and coordinates the federal government policy on the conversion to SI by federal agencies.Together NIST SP 330 and NIST SP 811 provide the legal interpretation of and guidelines for the use of the SI in the United States, as described in the Federal Register Notice PDF (May 16, 2008).
SI plays an essential role in international commerce and is the common language of scientific and technological research and development. The 2008 edition of NIST Special Publications (SP) 330, The International System of Units (SI), cover correct U.S. usage of metric units, such as the accepted spelling of "meter" and "liter". In addition, the revised guide includes a new chapter on units for quantities that describe biological effects, and symbols for expressing values for enzyme catalytic activity in Biology and Medicine.
Seven major changes have occurred from the 7th edition (1998) to the 8th edition (2006) of the SI Brochure and these changes have been incorporated into the 2008 edition of NIST SP 330:
NIST SP 330 is edited by Barry N. Taylor and Ambler Thompson, and can be requested in hard copy by contacting TheSI [at] nist.gov or downloading electronic copy here:
In another update, NIST Special Publication 811, Guide for the Use of the International System of Units (SI), complements SP330, and is published to assist NIST authors and others in correct SI usage and unit conversion. An extensive conversion factor appendix offers help in measurement unit conversions and in appropriate rounding-off of data. SP 811 also provides an editorial checklist for reviewing manuscripts' conformity with the SI and the basic principles of physical quantities and units. A color diagram has been added that illustrates the utilization of the SI base units in defining the 22 derived units with special names and symbols.
The U.S. Omnibus Trade and Competitiveness Act of 1988 designated "the metric system of measurement as the preferred system of weights and measures for United States trade and commerce." U.S. Public Law 110-69 in 2007, also known as the "American Competes Act" replaced the old definition of the metric system with the definition of the SI.
NIST SP 330 and NIST SP 811, both edited by Barry N. Taylor and Ambler Thompson, can be requested in hard copy by contacting TheSI [at] nist.gov or downloading electronic copies here:
Additional SI information can be found on the NIST Physics Laboratory website.
Further discussion of the Meter Convention, the SI, and international metrology may be found at the International Bureau of Weights and Measures (BIPM) website.