# S.I. Prefixes

The S.I. is the Systeme International. It is the accepted form in which units should be expressed so that the international scientific community can easily compare and comprehend results of experiments carried out in different countries.

All SI units except the one for mass (kg) have no prefix before them : J, m, N, Pa, V, A, C, W etc. (see the physics alphabet!)

The abbreviations below are those accepted by scientists all over the world as a 'short-hand' way of writing multiples of a value. The case of the letter matters a great deal as some letters in mean something very different when written in different cases.

e.g. 'm' represents a thousandth but 'M' represents a million times greater!  So 1MJ = 109 x 1mJ - the case of the letter is very important!

 Symbol Name Meaning Y yotta x 1024 multiplied by 1,000,000,000,000,000,000,000,000 Z zeta x 1021 multiplied by 1,000,000,000,000,000,000,000 E exa x 1018 multiplied by 1,000,000,000,000,000,000 P peta x 1015 multiplied by 1,000,000,000,000,000 T tera x 1012 multiplied by 1,000,000,000,000 G giga x 109 multiplied by 1,000,000,000 M mega x 106 multiplied by 1,000,000 k kilo x 103 multiplied by 1,000 c centi x 10-2 divided by 100 m milli x 10-3 divided by 1,000 μ micro x 10-6 divided by 1,000,000 n nano x 10-9 divided by 1,000,000,000 p pico x 10-12 divided by 1,000,000,000,000 f femto x 10-15 divided by 1,000,000,000,000.000 a atto x 10-18 divided by 1,000,000,000,000.000,000 z zepto x 10-21 divided by 1,000,000,000,000.000,000,000 y yocto x 10-24 divided by 1,000,000,000,000,000,000,000,000

You will need to use the abbreviations from 'Tera to femto' - throughout your school-life and they are also commonly used in everyday language...

kilogramme (1,000 grammes)

centimetre (a hundreth of a metre)

microscecond (a millionth of a second)

gigabyte (a thousand million bytes)

megaton (a million tons)

It is therefore well worth the effort to learn them properly and place them into your 'long term memory bank'!

Try some questions......?       Yes

How about learning to 'sing' the SI prefixes.... ?

....this activity is particularly good at Christmas time....