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GSC Guide to Authors The International System of Units
See also:
The International System of Units (Système international d'unités, abbreviated
SI in all languages), which is in use in most European countries, has been adopted
by Canada, and is popularly called the metric system. This system of weights,
measures, and physical quantities is decimal throughout.
The SI units are of three kinds: base, supplementary, and derived. There are
seven base units, one for each physical quantity, and two supplementary units
(Table 1). Derived units are obtained by the
multiplication and division of base and supplementary units. Several of these
derived units have been given special names and symbols (Table
2), and can be expressed in terms of other units and base units (Table
3). Table 4 gives examples of SI prefixes
and symbols. Several conversion factors are listed in
Table 5. Some units continue to be used with SI (Table
6), whereas other units should not be used (Table
7).
General rules for writing unit symbols, names, and numbers |
- The symbols are always in upright type, usually roman type.
- Symbols remain unaltered in the plural.
- Symbols are written without a period, except at the end of a sentence.
- When the symbol for a unit comprises letters, a full space is left between
the number and symbol, e.g. 45 kg, except when the first character
of a symbol is not a letter, e.g. 32°C.
- Symbols for SI units should always be used; unit names should not be written
out except in general terms such as several metres west. Names and
symbols should not be mixed.
- In North America, a period or dot is used as the decimal marker, and should
be positioned in line with the base of the numerals. Outside of North America
and in French text, the comma is used in place of the period.
- In numbers with many digits, the numbers are broken into readable blocks
of three digits each starting from the right and left of the decimal point,
e.g. 1 000 000. No space is left in a four-digit number
(e.g. 1000) except for uniformity where four-digit numbers occur
in tables.
- When a decimal fraction is used, a zero should always be placed to the left
of the decimal marker, e.g. 0.78 g.
Berkman, D.A. and Ryall, W.R. (ed.) |
1982: |
Field geologists' manual; Australasian Institute of Mining and Metallurgy,
Monograph Series no. 9 (second edition). |
|
Canadian Standards Association |
1980: |
Glossary of metric units; Canadian Standards Association, CSA Special
Publication, 2351-1980, Rexdale, Ontario, 57 p. |
1980: |
Metric editorial handbook; Canadian Standards Association, CSA Special
Publication Z372-1980, Rexdale, Ontario, 46 p. |
1989: |
Canadian metric practice guide; Canadian Standards Association, CAN/CSA-Z234.1-89
(reaffirmed 1995), Rexdale, Ontario, 82 p. |
|
National Bureau of Standards |
1977: |
The International System of Units (SI); National Bureau of Standards,
Special Publication 330, United States Government Printing Office, Washington
(translation of 'SI Le Système International d'Unités'). |
|
Royal Society of London |
1975: |
Quantities, units, and symbols; Royal Society of London, 54 p. (second
edition). |
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