Let $T_1, T_2, T_3, \dots \in \text{Exp}(\theta)$ each be an
D214: Exponential random positive real number such that
A
D5722: Random positive real number $X \in \text{Random}(0, \infty)$ is an
Erlang random positive real number with parameter $\theta$ if and only if
\begin{equation}
X
\overset{d}{=} \sum_{n = 1}^N T_n
\end{equation}