 Let's go over a little bit about positions in one dimension. So again, position is where an object is located, and it's always measured relative to some reference point. Because it's measured relative to a reference point, it ends up being a vector quantity, the magnitude, how far from the reference point, and the direction, which side of the reference point it is. It has a dimension of type length, and it always has standard units of meters. Because we're dealing with one dimension, that's its position along a line, but the lines could be horizontal lines or vertical lines. If it's a horizontal line, we typically use the variable x. If it's a vertical line, we typically use the variable y. But we're not always just talking about a single position, we might talk about a position function. And in this case, that means the position, as it varies with respect to time. If I were going to pronounce this equation, it's not x times t, or x multiplied by t, or anything like that. It's the position as a function of time, or x of t. Here's an example. The position as a function of time is 3 meters per second multiplied by the time, plus 2 meters per second squared multiplied by time squared. If I were to actually find the position at a specific time, I plug in that value for t into each place that t appears in the equation, multiply it all out, and find out that at two seconds, according to this particular equation, I've got a position of 14 meters. There's some special positions that we might need to pay attention to in our physics problems. One is our reference zero point. So if I'm thinking of my position as being along a line, and I've got numbers, where's my zero? Where's that reference point that I'm measuring everything with respect to? In some problems, it's really defined by the situation. So for example, you might be measuring everything relative to how far away it is from the wall, or how high something is above the floor. So it makes sense to use that fixed point, the wall or the floor, as your zero point. In other situations, you may be able to choose where your zero is, and a common choice is to start your zero at wherever your object started, or your initial position. Now when it comes to that initial position, there's a couple different ways you're going to see it written. One is an x with a sub i for the initial position. Another way to represent it is x sub zero for the zero position, particularly at time zero. And here we've got x as a function of time, and it's at specifically a time of zero. Now this x sub zero is also sometimes pronounced as x naught, where not, meaning nothing, is an old fashioned term representing zero. If we're talking about our final position, similar to our initial position, it's often abbreviated as x sub f for the final position. But it's also written out as x of t of f, or the position at the final time. So this just gives you an overview of some of the notation and special things to think about when we're dealing with positions in one dimension throughout the rest of this chapter.