 Here's an overview of notation in physics. When we're measuring real objects in their real properties, we refer to those as physical quantities. As we describe these physical quantities, we can describe them in three typical ways. We describe them in words, in symbols, and also as values. Starting with in words, this often comes from the word problem itself. It's an example the problem might talk about the mass of an object or the position of that particular object. But we need to make sure that our descriptions are clear. So for example with the mass, it might have to be the mass of a bowling ball or the mass of bowling ball number one in order to be completely clear what it is you're describing. Same thing for position, you might need to specify it's the position of car at three seconds. So we're describing what it is we're measuring of what objects and at what time. Now when we get into symbols, we need to do this to be able to use equations. So rather than the mass of the bowling ball number one, you've got m standing for that particular quantity. Be aware that in addition to our regular alphabet, we also use Greek letters. And it matters whether you're using uppercase or lowercase. Capital F and lowercase F might refer to two different things in the same problem. Also be aware that we often use subscripts. So if we're talking about that mass of the bowling ball or we're talking about an initial position or the position one, we might use subscripts to help keep those things separated. Which mass are we talking about? Which position are we talking about? Then we get into values. So sometimes you have known values. It might be six kilograms. It might be 18 meters or five seconds. And these are values that are known and given to you in a particular situation. Or it might be something that you're calculating nine meters per second. In any case, you need to make sure you have both a number and a unit. Now really all of these things are connected. So we don't want to think about a value as being separate from a symbol and the symbol being separate from the words. As you're describing something, that six kilograms is the mass of the bowling ball. And we use the symbol m sub b to describe that. If you're careful on your notation, then it's going to be much clearer what you're doing in your problem solving solution. Both to communicate it to other people and to keep track of things for yourself. So keep in mind all of this notation is physics as you work throughout the rest of your course.