100 Words Every High School Freshman Should Know
by Editors of The American Heritage Dictionaries (Editor)
kil·o·me·ter (k-lm'-tr or kl'-m'tr)
A unit of length equal to 1,000 meters or 0.62 of a mile.
Note: The metric system is a system of measurement that is based on the number 10. Because 12 inches make a foot, and 3 feet make a yard, calculating the number of inches in a given number of yards or miles can often be cumbersome. In the metric system, multiplication is easy. Kilo- is a prefix meaning "a thousand," so one kilometer is equal to a thousand meters, and one kilogram is equal to a thousand grams. Likewise, if you know something is 18 kilometers away, you can easily calculate that it's 18,000 meters away.
Some common prefixes in the metric system are:
milli- "one thousandth"
kilo- "one thousand"
centi- "one hundredth"
cento- "one hundred"
deci- "one tenth"
The basic units of measurement in the metric system are the gram, for weight; the liter, for volume; and the meter, for distance. The prefixes can be combined with these units to form different measurements: a centigram is a hundredth (1/100) of a gram; a milliliter is a thousandth (1/1000) of a liter.
But the metric system isn't limited to these units: a kilowatt is a thousand watts, and a millisecond is a thousandth of second.
There are even more prefixes for larger and smaller units!
micro- "one millionth"
mega- "one million"
nano- "one billionth"
giga- "one billion"
pico- "one trillionth"
tera- "one trillion"