What value signifies an event that cannot occur in probability terms?

In probability, values are assigned to events to quantify their likelihood of occurrence. A probability of 0 explicitly indicates that an event cannot occur; it is impossible. For example, if you were to assign a probability of 0 to an event such as rolling a seven with a standard six-sided die, that reflects that this event simply cannot happen.

In contrast, a probability of 1 signifies certainty, meaning the event is guaranteed to occur, while a probability of 0.5 indicates that the event has an equal chance of occurring or not occurring. An undefined probability does not apply in standard contexts, as all events should be assigned probabilities ranging from 0 to 1. Therefore, the correct identification of a value representing an event that absolutely cannot occur is indeed 0.