You are probably already familiar with the following conversions:
|milli (m)||1/1000 or one thousandth|
|centi (c)||1/100 or one hundredth|
|kilo (k)||1000 or one thousand|
So "1 millimetre" literally means "one thousandth of a metre".
Learning the S.I. units now becomes more of a language lesson than a mathematics lesson! The next page shows the various prefixes that one is likely to come across while working with measured quantities.
As you are reading through this table, notice that all the prefixes are multiples of ten. This is one of the key properties of the SI system - it is a decimal system.