 When we're measuring very large quantities or very small quantities, they're usually much more convenient to attach a prefix to the quantity. So this table lists some of the common prefixes that we'll see in data communications and networking. For example, kilo or lowercase k is a factor of 10 to the power of 3 or 1000. 1 kilogram is equal to 10 to the power of 3 grams or 1000 grams. And going up, we have mega, an uppercase m, 10 to the power of 6, or a factor of 1 million, sorry, giga, 1 billion, tera, 10 to the power of 12. And they're further as we go up. And dealing with smaller quantities, we often use milli, 10 to the power of minus 3, micro, nano and picot. So if you can remember these different prefixes and the factors that they use, then that's a good start for understanding and seeing their use in communications and networking. Note, of course, the factors differ by a factor of 10 to the power of 3 or 1000. So kilo, 10 to the power of 3, going up to mega, 10 to the power of 6, 10 to the power of 9, 12. And same going down, 10 to the power of minus 3, minus 6, minus 9, minus 12. So very easy to remember those factors. As an example, if we have a quantity of some power level, let's say 20 kilowatts, then kilo, the k means 10 to the power of 3. So we get 20 times 10 to the power of 3 watts or 20,000 watts or .02 megawatts. Another example, if we have half a second, then what is that in milliseconds? Well, half a second is 5 by 10 to the minus 1 seconds, which is the same as 500 by 10 to the power of minus 3 seconds. Because 500 is 5 by 10 to the power of 2, times by 10 to the power of minus 3 is 10 to the power of minus 1, which is 500 milliseconds. Because milli, lowercase m, has a factor of 10 to the power of minus 3. So you should be able to easily do conversions between using with different quantities and when different prefixes are in use.