This Demonstration presents the formal definition of the limit of a function, for in-class use by instructors. It allows the instructor to "challenge" students to find a suitable delta , first for some particular value of epsilon , and subsequently in general for an arbitrary epsilon (see [1] for an example of the intended pedagogical approach). Roman letters and are used instead of Greek letters and in order to reduce cognitive load for students encountering the concept of a limit for the first time.