Prefixes in SI Units

The metric system has been adopted almost around the world. 

But, over the time, a number of other units (multiples and submultiples of the SI units) have come into use. 

This has happened because the SI units of some physical quantities are either too big or too small. 

The units smaller or bigger than those based on metric system are related to the metric unit by the powers of 10. 

Different powers of 10 are indicated by prefixes.

For example, one hundredth part (10^–2) of a metre is called centimetre: centi means one-hundredth.

A list of standard prefixes is given here.