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# What Do Prefixes Mean in Math? - Part 1

Learn what math prefixes like “milli,” “kilo,” “mega,” and “giga” mean, where they come from, and whether or not more prefixes will be added in the future.

By
Jason Marshall, PhD
Episode #38

http://www.shutterstock.comWe use a lot of math words in our day-to-day lives without really understanding what they mean or where they come from. For example, prefixes like “mega,” “giga,” and “tera” that we use to describe computer hard drive sizes (think “megabyte,” “gigabyte,” and “terabyte”) have specific meanings and uses that go far beyond the world of computers. So today we’re taking some time to explore the language of mathematical prefixes.

## The Metric System of Units and Prefixes

To start things off, let’s take a minute to talk about the different systems of units commonly used around the world for making measurements. The first system is called the imperial system and uses units of miles, yards, feet, and inches for measuring distances. This system is quite familiar to you if you grew up in the US, but probably not so much if you grew up almost anywhere else. And that’s because the main system of units used around the world—including by nearly all scientists and mathematicians—is called the SI system (which stands for “International System”), or more commonly, the metric system. Why is the metric system so popular? Well, in many ways it’s because of its simplicity. So why is it so simple? One word: prefixes. Here’s what I mean.

According to an international agreement first made in 1795, the metric unit of distance is the meter, and that means that all other lengths measured in the metric system are based on the meter. You’re already quite familiar with this fact since you’ve seen meter sticks divided up into centimeters and millimeters, and you’ve measured longer distances in kilometers. What’s the common feature in all these words: centimeters, millimeters, kilometers? Of course it’s the “meter” part. So what’s going on here? Well, that international agreement that established the length of the meter in 1795 also established a group of six prefixes that could be tacked onto the unit meter to modify its meaning.

## Prefixes for Numbers Smaller Than One

Those original six prefixes were

• milli,

• centi,

• deci,

• deca,

• hecto, and

• kilo.