\begin{definition}[Definition:Modulus (Geometric Function Theory)]
In geometric function theory, the term '''modulus''' is used to denote certain conformal invariants of configurations or curve families.
More precisely, the modulus of a curve family $\Gamma$ is the reciprocal of its extremal length:
:$\mod \Gamma := \dfrac 1 {\map \lambda \Gamma}$
\end{definition}