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The definition of an axis in math is a number line that implies motion through positive numbers, negative numbers and zero as mapped on a graph. Define an axis, such as an x-axis and a y-axis, with instructions from a college-level math teacher in this free video on geometry.

So, what is the definition of an axis in math? Hi, I'm Jimmy Chang, I've been teaching college math for 9 years. And an axis in math is something that is used often in the various algebra courses in geometry as well as calculus, it all depends on what the situation happens to be. Now most college courses use just the two axis, that which we'll discuss very shortly, and calculus ends up using a third axis, we can picture the third axis but it's kind of hard to graph. But before we get too ahead of ourselves lets talk about what an axis in math actually is. It's actually a number line, but that this indicates giving motion with positive and negative numbers and the number zero. Now here's some examples. Let's talk about the X axis. The X axis is a horizontal axis, it gives you motions that deal with right or left. Now the middle is 0, and over here represent positive numbers, like 1, 2, 3 and 4, and over here, negative numbers, negative 1, negative 2 and so on. There's also the Y axis, which is another number line, but you can think about it in a vertical standpoint. That's why the Y axis can be construed sometimes as a vertical number line, because it operates the same way, except it gives you vertical motions, upward or downward. Now the middle is 0, but above it you have positive 1, positive 2, positive 3, positive 4, positive 5, of course so on and so forth. And below the 0 you have negative 1, negative 2, negative 3, negative 4, and of course the pattern continues on. So, so far you have the X axis giving you the horizontal motions with positive and negative values in 0, and the Y axis which gives you the vertical motions, positive, negative and zero. Now there's a third axis known as the Z axis. I only mention this briefly here, but it works the same idea. The Z axis gives you that third dimension, it gives you the diagonal axis, you can go diagonally negative or diagonally positive and you label it the same way. But you have three axis, three motions, and my name is Jimmy Chang, and that's how you define an axis in math.