The International System of Units, universally abbreviated SI (from the French Le Systême International d'Unitês), is the modern metric system of measurement. Long the dominant system used in science, the SI is rapidly becoming the dominant measurement system used in international commerce.
In recognition of this fact and the increasing global nature of the marketplace, the Omnibus Trade and Competitiveness Act of 1988, which changed the name of the National Bureau of Standards (NBS) to the National Institute of Standards and Technology (NIST) and gave to NIST the added task of helping US industry increase its competitiveness, designates "the metric system of measurement as the preferred system of weights and measures for United States trade and commerce."
The definitive international reference on the SI is a booklet published by the International Bureau of Weights and Measures (BIPM, Bureau International des Poids et Mesures) and often referred to as the BIPM SI Brochure. Entitled Le Systême International d'Unitês (SI), the booklet is in French followed by a text in English. This 2008 edition of NIST Special Publication (SP) 330 is the United States version of the English text of the eighth edition of the Brochure (the most current) published in 2006. The 2008 edition of NIST SP 330 replaces its immediate predecessor, the 2001 edition, which was based on the seventh edition of the BIPM SI Brochure published in 1998, but including Supplement 2000: addenda and corrigenda to the 7th edition (1998), published by the BIPM in June 2000.
Like its 2001 predecessor, the 2008 edition of NIST SP 330 conforms with the English text in the BIPM SI Brochure but contains a few minor differences to reflect the most recent interpretation of the SI for the United States by the Secretary of Commerce, as published in the Federal Register of July 28, 1998, 63 FR 40334-40340 (The Metric Conversion Act of 1975 gives the Secretary of Commerce the responsibility of interpreting or modifying the SI for use in the United States. A slightly updated version of the 1998 interpretation is expected to be published in the Federal Register in 2008). These differences include the following:
- The spelling of English words is in accordance with the United States Government Printing Office Style Manual, which follows Webster's Third New International Dictionary rather than the Oxford Dictionary. Thus the spellings "meter," "liter," and "deka" are used rather than "metre," "litre," and "deca" as in the original BIPM English text.
- The name of the unit with symbol t and defined according to 1 t = 103 kg is called "metric ton" rather than "tonne".
- The four units curie, roentgen, rad, and rem are given in Table 10, p. 38.
- A number of "Editors notes" are added in order to indicate such differences where significant (except spelling differences) and to clarify the text.
- A few very minor editorial changes are made in order to "Americanize" some phrases.
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