\begin{definition}[Definition:Derivative/Complex Function/Point]
Let $D\subseteq \C$ be an open set.
Let $f : D \to \C$ be a complex function.
Let $z_0 \in D$ be a point in $D$.
Let $f$ be complex-differentiable at the point $z_0$.
That is, suppose the limit $\ds \lim_{h \mathop \to 0} \ \frac {\map f {z_0 + h} - \map f {z_0} } h$ exists.
Then this limit is called the '''derivative of $f$ at the point $z_0$'''.
It can be denoted $f' \left({z_0}\right)$, 
Category:Definitions/Complex Analysis
\end{definition}