5 . 2 s i d e r i v e d u n its A derived unit is a unit of measurement of a derived quantity in a given system of quantities [4]. SI derived units are derived from the SI base units in accordance with the physical connection between the quantities. Example:
From the physical connection between the quantity length measured in the unit m, and the quantity time measured in the unit s, the quantity speed measured in the unit m/s can be derived.
Derived units are expressed in base units by use of the mathematical symbols multiplication and division. Examples are given in Table 4. The CGPM has approved special names and symbols for some derived units, as shown in Table 5. Some base units are used in different quantities, as shown in Table 6. A derived unit can often be expressed in different combinations of 1) base units and 2) derived units with special names. In practice there is a preference for special unit names and combinations of units in order to distinguish between different quantities with the same dimension. Therefore a measuring instrument should indicate the unit as well as the quantity being measured by the instrument.
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