So the L right over here actually does stand for linear, and here, the condition is is that the actual relationship in the population between your X and Y variables actually is a linear relationship. So actual linear relationship between X and Y. Now, in a lot of cases, you might just have to assume that this is going to be the case when you see it on an exam, like an AP exam, for example. They might say, hey, assume this condition is met. Oftentimes, they'll say, assume all of these conditions are met. They just want you to maybe know about these conditions, but this is something to think about. If the underlying relationship is nonlinear, well, then maybe some of your inferences might not be as robust.