So let's say this right over here is our position. So I'll call that the S axis, S for position. And that's going to be in miles. And S is, it's, you know, obviously, S doesn't really stand for position, but P, you know, it kind of looks like rho for density, and D we use for differentials, or distance, or displacement. So S is what gets used for position very often. So let's say S is our position. And let's see, this is T for time.