In the last video, we tried to come up with a somewhat rigorous definition of what a limit is, where we say when you say that the limit of f of x as x approaches c is equal to l, you're really saying, and this is a somewhat rigorous definition, that you can get f of x as close as you want to l by making x sufficiently close to c. So let's see if we can put a little bit meat on it. So instead of saying as close as you want, let's call that some positive number epsilon. So I'm just going to use the Greek letter epsilon right over there. So it really turns into a game. So you tell me how close you want. So this is the game. You tell me how close you want f of x to be to l. And you do this by giving me a positive number that we call epsilon, which is really how close you want f of x to be to l. So you give a positive number epsilon.