\begin{definition}[Definition:Koebe Constant]
The Koebe Quarter Theorem states:
{{:Koebe Quarter Theorem}}
That constant $\dfrac 1 4$ by which $\size {\map {f'} 0}$ is bounded below can be found referred to as the '''Koebe constant'''.
{{NamedforDef|Paul Koebe|cat = Koebe}}
\end{definition}