So one way to think about it, one way to think about it is this is the instantaneous, this is the rate right on the margin at which our cost is changing with respect to quantity. So if I were to produce just another drop, another atom of whatever I'm producing, at what rate is my cost going to increase? And the reason why I'm saying it right on the margin is we see that it's not constant. If our cost function were a line, we would have a constant slope. The tangent line would essentially be the cost function. But we see it changes right over here. The incremental atom to produce here costs less than the incremental atom right over here.