Let $P = (\Omega, \mathcal{F}, \mathbb{P})$ be a D1159: Probability space such that

(i)	$E \in \mathcal{F}$ is an D1716: Event in $P$

Let $\log_a$ be the D866: Standard real logarithm function in base $a \in (0, \infty)$ such that

(i)	\begin{equation} \log_a 0 : = - \infty \end{equation}

The Shannon information of $E$ in $P$ in base $a$ is the D5237: Unsigned basic number \begin{equation} - \log_a \mathbb{P}(E) \in [0, \infty] \end{equation}