Definition:Event/Occurrence/Equality

Definition
Let the probability space of an experiment $\EE$ be $\struct {\Omega, \Sigma, \Pr}$. Let $A, B \in \Sigma$ be events of $\EE$ such that $A = B$.

Then:
 * the occurrence of $A$ inevitably brings about the occurrence of $B$

and:
 * the occurrence of $B$ inevitably brings about the occurrence of $A$.

Also see

 * Definition:Impossible Event