Council Directive of 20 December 1979 on the approximation of the laws of the Member States relating to units of measurement and on the repeal of Directive 71/354/EEC (80/181/EEC)

[X11.3. Prefixes and their symbols used to designate certain decimal multiples and submultiples U.K.
[F1Factor Prefix Symbol
10 24 yotta Y
10 21 zetta Z
10 18 exa E
10 15 peta P
10 12 tera T
10 9 giga G
10 6 mega M
10 3 kilo [X2k]
10 2 hecto [X2h]
10 1 deca da
10 -1 deci d
10 -2 centi c
10 -3 milli m
10 -6 micro μ
10 -9 nano n
10 -12 pico p
10 -15 femto f
10 -18 atto a
10 -21 zepto z
10 -24 yocto y]

The names and symbols of the decimal multiples and submultiples of the unit of mass are formed by attaching prefixes to the word ‘ gram ’ and their symbols to the symbol ‘ g ’ .

Where a derived unit is expressed as a fraction, its decimal multiples and submultiples may be designated by attaching a prefix to units in the numerator or the denominator, or in both these parts.

Compound prefixes, that is to say prefixes formed by the juxtaposition of several of the above prefixes, may not be used.]

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