The Metric System
The metric system, or International System, is the world's mostused measurement system and the preferred system for scientists. Its abbreviation is S.I., which stands for the French Système Internationale, meaning International System.
The metric system can be used to measure many things, from mass to volume, and the best part is that all the measurements are in base 10 which makes it easy to remember.
This system uses a basic unit of measurement, the meter. A meter is about as long as one yard. Now, to find out how many meters we are talking about, we need to see the first part of the word. For example, the word kilometer.
We can dissect kilometer into two parts that each have a different meaning. In this case kilometer. We've already discussed the meter, but what does “kilo” mean? Well, the prefix means one thousand, so whenever you hear “kilo” in front of a word, you can tell that means one thousand of whatever's being talked about.
Here's a handy list of all the prefixes and their meanings:
Kilo – 1000
Hecto – 100
Deka – 10

Deci – 0.10, 1/10
Centi – 0.01, 1/100
Milli – 0.001, 1/1000
Simple, right?
The same prefixes apply to any units of the metric system, whether it be meters (length), grams (mass), newtons (weight), or liters (volume).