What measurement comes before miles?

A kilometer is one thousand TIMES a meter (1 meter X 103) and a megameter is one million TIMES a meter (1 meter X 106), while a millimeter is one thousANDTH of a meter (1 meter X 10-3) and a micrometer is one millionTH of a meter (1 meter X 10-6).

The prefix (e.g. kilo) attached to the unit (e.g. meter) defines the multiplier, as in kilo means "1000 times" and mega means "million times," while millimeans "1/1000 of" and micro means " one millionth of." So, for example, kilometer can broken down into kilo and meter, suggesting 1000 times a meter, which is equal to 1000 meters.

The prefix either breaks a unit (in this case meters) into parts of the unit or multiplies of the unit, depending on the SIGN (+ or -) of the exponent attached to the prefix (negative exponents refer to fractions of the unit [smaller] while positive exponents refer to multiples of the unit [bigger]). All common prefixes are listed here (courtesy of http://www.unc.edu/~rowlett/units/prefixes.html):

yotta- (Y-)

1024

1 septillion

zetta- (Z-)

1021

1 sextillion

exa- (E-)

1018

1 quintillion

peta- (P-)

1015

1 quadrillion

tera- (T-)

1012

1 trillion

giga- (G-)

109

1 billion

mega- (M-)

106

1 million

kilo- (k-)

103

1 thousand

hecto- (h-)

102

1 hundred

deka- (da-)**

10

1 ten

deci- (d-)

10-1

1 tenth

centi- (c-)

10-2

1 hundredth

milli- (m-)

10-3

1 thousandth

micro- (µ-)

10-6

1 millionth

nano- (n-)

10-9

1 billionth

pico- (p-)

10-12

1 trillionth

femto- (f-)

10-15

1 quadrillionth

atto- (a-)

10-18

1 quintillionth

zepto- (z-)

10-21

1 sextillionth

yocto- (y-)

10-24

1 septillionth