The concept of the limit is one of the most crucial things to understand in
order to prepare for calculus. A limit is a number that a function approaches
as the independent variable of the function approaches a given value. For
example, given the function *f* (*x*) = 3*x*, you could say, "The limit of *f* (*x*) as
*x* approaches 2 is 6." Symbolically, this is written *f* (*x*) = 6. In the following sections, we will more carefully define a limit, as well
as give examples of limits of functions to help clarify the concept.

Continuity is another far-reaching concept in calculus. A function can
either be continuous or discontinuous. One easy way to test for the continuity
of a function is to see whether the graph of a function can be traced with a pen
without lifting the pen from the paper. For the math that we are doing in
precalculus and calculus, a conceptual definition of continuity like this one is
probably sufficient, but for higher math, a more technical definition is needed.
Using limits, we'll learn a better and far more precise way of defining
continuity as well. With an understanding of the concepts of limits and
continuity, you are ready for calculus.