The SI units have been adopted in almost all countries. The SI units of certain physical quantities are either too big or too small. As a result, a number of other units, multiples and submultiples of the SI units, have to come into use. These multiples and submultiples are related to the base SI units by powers of 10. Different powers of 10 are indicated by prefixes. For example one hundredth part (10 -2) of a meter is called a centimeter: centi means one hundredth. The prefix kilo means one thousand: one kilogram means one thousand grams.