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# What Do Prefixes Mean in Math? - Part 2

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

By
Jason Marshall, PhD,
October 14, 2010
Episode #039

Page 1 of 2

http://www.shutterstock.comA few weeks ago, we began talking about the meaning of prefixes in math. In particular, we talked about the prefixes used in the metric system to represent lengths smaller than one meter. Today, we’re going to continue this topic by talking about the metric prefixes used to describe lengths much longer than one meter. And, since we’re chatting about big numbers, we’ll also talk a bit about the future of a recently proposed prefix for describing really big numbers.

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## Review of Metric Prefixes

In the first part of this series, we introduced some of the logic behind the metric system of units—that is, the system of units established in 1795 and now used by the majority of the world to measure lengths in meters, centimeters, millimeters, and a bunch of other units based upon the meter. We also talked about the fact that this whole system of units has been extended by using a set of internationally agreed upon prefixes. In particular, we talked about the various prefixes used to break the meter up into smaller pieces. For example, a centimeter is one-hundredth of a meter, a millimeter is one-thousandth of a meter, the micrometer and nanometer are one-millionth and one-billionth of a meter, and there are more almost unfathomably tiny lengths continuing on from there.

But why do we need these other units? Why aren’t all lengths just measured in meters? Well, it’s simply because they make it a lot easier to write and talk about really small lengths. For example, it’s a lot easier to say that a typical human hair is between 20 and 80 micrometers long, rather than to say that it’s between 0.00002 and 0.00008 meters long—wouldn’t you agree?

## The Original Six Metric Prefixes

We’ve also talked about the fact that the original six prefixes defined for use in 1795 were:

• “milli,”

• “centi,”

• “deci,”

• deca,”

• “hecto,” and

• “kilo.”

We’re familiar with three of these (“milli,” “centi,” and “kilo”), but I bet most of you have never even heard of “deci,” “deca,” and “hecto”—until recently, I hadn’t either! And that’s simply because they’ve long fallen out of favor. But what were they originally intended for? Well, the decimeter represents a length of one-tenth of a meter (that is, 10 centimeters), the decameter represents a length of 10 meters, and the hectometer represents a length of 100 meters. My guess is that people found it plenty convenient to say that something is 30 centimeters, and didn’t really need the option of calling it 3 decimeters too.