\begin{definition}[Definition:Gamma Function/Weierstrass Form]
The '''{{AuthorRef|Karl Theodor Wilhelm Weierstrass|Weierstrass}} form''' of the '''gamma function''' is:
:$\ds \frac 1 {\map \Gamma z} = z e^{\gamma z} \prod_{n \mathop = 1}^\infty \paren {\paren {1 + \frac z n} e^{-z / n} }$
where $\gamma$ is the Euler-Mascheroni constant.
The '''Weierstrass form''' is valid for all $\C$.
\end{definition}