\begin{definition}[Definition:Event/Occurrence/Impossibility]
Let the probability space of an experiment $\EE$ be $\struct {\Omega, \Sigma, \Pr}$.
Let $A \in \Sigma$ be an event of $\EE$ whose probability of occurring is equal to $0$.
Then $A$ is described as '''impossible'''.
That is, it is an '''impossibility''' for $A$ to occur.
\end{definition}