The Metric System - Greek Numerical Prefixes

The Systèm International d'Unités (SI) is a system of units for the measurement of physical quantities that has been almost universally adopted (the U.S.A. and a few obscure countries still use older Imperial measurement systems). It uses Greek-derived prefixes to indicate multiples and submultiples in order to avoid a multiplicity of zeros when expressing very large or very small metric amounts. The following is a list of prefixes along with the standard abbreviations and factors of the numbers:

Prefix	Abbreviation	Factor
vendeka-	V	10 33 (decillion)
xenna-	X	10 27 (octillion)
yotta-	Y	10 24 (septillion)
zetta-	Z	10 21 (sextillion)
exa-	E	10 18 (quintillion)
peta-	P	10 15 (quadrillion)
tera-	T	10 12 (trillion)
giga-	G	10 9 (billion)
mega-	M	10 6 (million)
kilo-	k	10 3 (thousand)
hecto-	h	10 2 (hundred)
deca-	da (or sometimes D)	10 1 (ten)
deci-	d	10 -1 (tenth)
centi-	c	10 -2 (hundredth)
milli-	m	10 -3 (thousandth)
micro-	μ	10 -6 (millionth)
nano-	n	10 -9 (billionth)
pico-	p	10 -12 (trillionth)
femto-	f	10 -15 (quadrillionth)
atto-	a	10 -18 (quintillionth)
zepto-	z	10 -21 (sextillionth)
yocto-	y	10 -24 (septillionth)
xenno-	x	10 -27 (octillionth)
vendeko-	v	10 -33 (decillionth)

Note that the hecto-, deca-, deci-, and centi- prefixes are typically used only if the milli- or kilo- prefixes would be impractical for measuring numbers used in the "real world". For example, we might say 28 centimetres instead of 280 millimetres. As well, the more extreme prefixes are rarely used (simply expressing the measurements using scientific notation is usually just as easy).

If you're interested in the Ancient Greeks (who had nothing to do with the metric system; the developers of the metric system just borrowed some of their words), see the Ancient Greek timeline.