 Consider this program, which calculates a person's approximate age and days. There's nothing wrong with it. It works great when we run it. However, the variable names Y and D leave something to be desired. If we had a very long program with lots of variables, we wouldn't really know what D stands for. Does it stand for days, discount, deposit? Who would know? You should always make your variable names as meaningful as possible. In this program, changing Y to years and D to days makes the program more readable with a minimum of effort. Suppose we wanted to be a bit more specific and name the variable for the age in years and the age in days. If we used variable names like this for age in years and age in days, this would be a terrible way of doing it. The names are far too short, the first one is totally meaningless, and the second one looks like a call for help. We could spell out the name entirely, but these names are very difficult to read. So how do you handle multi-word variable names? You could spell out the name entirely, but these names are very difficult to read. One method, which is the one that is used by convention in Java and JavaScript, is called camel case, where each word after the first in a multi-word variable name is capitalized. It's called camel case because the capital letters are supposedly reminiscent of the humps of a camel. Well, it does if you have a terrific imagination. Another solution is to use underscores between the words in a variable name. This is called snake case because the underscores make the word look sort of like the segments of a snake's body, again with a lot of imagination on your part. This is the convention that most sea guidelines recommend for variable and function names. The book we're using at the time that these videos were recorded uses camel case, but I'll use snake case for most of these videos. When naming your variables, don't make the names too short. And don't make them ridiculously long. Make them just the right size.