For example, if someone were to say, what is the limit of f of x as x approaches four, well, then we could think about the two one-sided limits, the one-sided limit from below and the one-sided limit from above. So we could say, well, let's see. The limit of f of x as x approaches four from below. So let me draw that. So we care about x equals four. As x equals four from below, so when x equals three, we're here where f of three is negative two. f of 3.5 seems to be right over here.