@Moros:
In english scheveningen would make the right pronounciation.
@warflowvet:
Derivatives are the fundament of analysis. Since you ask about derivatives I'll assume you know what is a limit in mathematics. A derivative is basically a function that shows how another functions grow locally. It is easiest to look at them in on dimention, so by definition:
The function f' is defined by the following limit (if it exists) in point x0 for a given function f. If you look at the formula it basicaly compares the growth of function (the numerator) to the growth in the argument of function (denominator) on a very small scale. In other words it tells us how the function "behaves" locally. Let us consider an example with a standard f(x)=x^{2}
In this example we see that the growth of f behaves like a linear function 2x. For example at point x_{0}=2 f'(x)=4, so that means that at point 2 function f behaves like a linear function g(x)=4x locally. That is the easiest explanation I can come up with, it should suffice provided you know what a limit is. Sorry for bad quality of LaTeX, but I couldn't find a better online render to jpg.
