A 2 dimensional space is called a plane. It is a 'lines worth of lines,' to put it one way. Again, with the plane we don't want our 3 full dimensions, so we'll have to say that the plane has no height (saying it has no width is okay too, but then we'd have to say it has length and height).



We need to find a way to describe points in the plane. You can picture 2 number lines inside the plane that intersect at a right angle. In algebra class we might learn to call one of these, the horizontal one, the x-axis and the other, the vertical, the y-axis. Having specified an order (x first, then y), we can then describe any point by two numbers. For example (6,-2.8) is the point that is 6 units (a "unit" in this context is just the length from 0 to 1) in the x-direction and -2.8 units in the y-direction.



Which point have we described?