A metric prefix is a word which is added to the beginning of a base unit to show a multiple of that unit. All metric prefixes are powers of 10. Metric prefixes can be considered as an alternative to the scientific notation. For example, 7.3* 10^3 grams can be written as 7.3 kilograms since the prefix kilo means 10^3. 7.3 * 10^3 grams = 7.3 kilograms Each metric prefix has a unique symbol that can precede any unit symbol.

Metric Prefixes Greater Than 1
Prefix	Symbol	Power
peta	P	10^(15)
tera	T	10^(12)
giga	G	10^9
mega	M	10^6
kilo	k	10^3
hecto	h	10^2
deca	da	10^1

Notice that the symbols for the prefixes greater than 1 are uppercase letters, except for kilo, hecto, and deca. There is no prefix used for 10^0=1. The metric prefixes less than 1 are shown in the following table.

Metric Prefixes Less Than 1
Prefix	Symbol	Power
deci	d	10^(- 1)
centi	c	10^(- 2)
milli	m	10^(- 3)
micro	μ	10^(- 6)
nano	n	10^(- 9)
pico	p	10^(- 12)
femto	f	10^(- 15)

Note that the prefix names cannot be used together. 2 * 10^(- 9) meters 2 nanometers 2 millimicrometers Another important note is that the International System of Units base unit of mass, kilogram, already contains a prefix. Since multiple prefixes are not allowed, the prefix names shown in the tables are used with the unit gram (g). 10^(- 6) kilograms 1 milligram 1 microkilogram