 In this video, I'm going to show you how to work with some of the SI prefixes. To start with, what does SI stand for? That's the System Internationale. It's the French acronym for the International System of Units, which is used everywhere except in the US. And even in English, we use the French version SI. We don't turn it to IS, International System, but it's System Internationale. So I have here a couple of the common prefixes you will find every now and then. They're used with SI units, but they're also used with non-SI units. If we start at the top, here for example, we have the capital G, which stands for Giga. You probably have heard this as one gigabyte, or one GB. Now, what is the meaning of this? Well, one gigabyte is equal to thousand megabyte, which is going to be the next one. That means this one here, I could just erase my Giga and replace this by thousand mega, multiply it. So what I get is one times thousand, one gigabyte is thousand megabyte. So far, let's go to the next one, the mega. One mega is thousand kilo. So if we go again with computers, if you have, let's say, 100 megabytes of free space on your hard drive, it's not as much anymore. You can simply replace the mega here by thousand K, and you get that we have 100 times thousand kilobytes. Next one, the kilobyte, or the kilo for the prefix around. One kilo means simply it's thousand. Well, you might have heard if you continue with IT that, well, the one kilobyte, what's one kilobyte? One kilobyte is a thousand bytes. Now, I want to change it because the kilo you probably hear this more with kilometers. So what does one kilometer stand for? The kilo here is the thousand. So this is one times thousand meters. So one kilometer is thousand meters. Next one important once is the desi. Here it really helps if you know some French, because what does the desi stand for? It's like this 10. So it's one over 10. An example, for example, we have a glass of two desi liters, liters not really SI unit, but uses the same style of prefixes. So what does that mean? That this is two times one over 10 liters. So 0.2 liters is two desi liters. Next one, the C stands for centi. Again, French helps. The number centi, so this is one over 100. So it's 100. So let's go with a centimeter. So what is a centimeter? A centimeter is literally one times one over 1000, one over 100. Sorry, I'm replacing the C with its equivalence, the one over 100 meter. So 0.01 meter is one centimeter. And then the last one in this table, the M is the mille, mille from French again. So you have one over 1000 over here. And what should we use? Let's go with milliliters again. So let's say one milliliter. How much is one milliliter? Well, the M stands for one over 1000. So one milliliter is equal to one times one over 1000 liters. Now, there are many more. Just look them up on the internet and put them on a cheat sheet somewhere, or on the long run, you might want to memorize them. These are probably the most common ones, like the kilo, the desi, the centi, and the mille. There are even some Greek symbols that are used, but don't get too confused about it. For example, there is this little thing, it's called a micro, like a big leg here, and then a little bit like a U micro. And this is one over a million. One, two, three, four, five, six zeros. And then the next lower one would be the nano. Now we get back to Latin letters, nano. And French can help again because nano is like nine. So that will be one with nine zeros. So this is equal to one over one, one, two, three, four, five, six, seven, eight, nine. Nine zeros is to nano. And as I say, there are many more. Just look them up on the internet and kind of make yourself a little cheat sheet. Sometimes the calculators even have cheat sheets included on the back somewhere. So in my class, you're welcome to use those cheat sheets. If you're with another teacher, ask your teacher if he would allow it.