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!
You will need to use these abbreviations 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)
Try some questions......? Yes
How about learning to 'sing' the SI prefixes.... this activity is particularly good at Christmas time....