Cardinal Number zero must be distinguished from Real Number zero. The real number zero is a limit, this being why an event with probability zero can occur, e.g. a coin can land on a region r such that r is one of infinitely many regions where the coin could possibly land. This is because an event 'with probability zero' is one whose probability is minimal, not non-existent. But the cardinal number zero is not a limit; it is the size of a set. More precisely, it is the size of a set that has no members. Since limit-zero means 'minimal', as opposed to 'non-existent', an event can happen even its probability is real-number zero.