The International System of Units (SI) is founded on seven SI base units for seven base quantities assumed to be mutually independent, as given in Table 1. Here is the SI list from the NIST reference on Constants, Units and Uncertainty.
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Table 1. SI base units |
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For detailed information on the SI base units, see Definitions of the SI base units and their Historical context.
SI derived units
Other quantities, called derived quantities, are defined in terms of the seven base quantities via a system of quantity equations. The SI derived units for these derived quantities are obtained from these equations and the seven SI base units. Examples of such SI derived units are given in Table 2, where it should be noted that the symbol 1 for quantities of dimension 1 such as mass fraction is generally omitted.
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Table 2. Examples of SI derived units |
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| SI derived unit
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| Derived quantity | Name | Symbol |
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| area | square meter | m2 |
| volume | cubic meter | m3 |
| speed, velocity | meter per second | m/s |
| acceleration | meter per second squared | m/s2 |
| wave number | reciprocal meter | m-1 |
| mass density | kilogram per cubic meter | kg/m3 |
| specific volume | cubic meter per kilogram | m3/kg |
| current density | ampere per square meter | A/m2 |
| magnetic field strength | ampere per meter | A/m |
| amount-of-substance concentration | mole per cubic meter | mol/m3 |
| luminance | candela per square meter | cd/m2 |
| mass fraction | kilogram per kilogram, which may be represented by the number 1 | kg/kg = 1 |
Table 3. SI derived units with special names and symbols
Table 4. Examples of SI derived units whose names and symbols include SI derived units with special names and symbols
For Table 3 and Table 4, click here.