There are two important properties of probability.

• The probability of an event E is between 1 and 0, i.e., 0 < P(E) < 1.
• The sum of probabilities of all mutually exclusive and exhaustive events is equal to 1.

These two properties together define probability.

When we roll a die, the events 1, 2, 3, 4, 5, and 6 are mutually exclusive and exhaustive. The probability of any event occurring is between 0 and 1. The sum of probabilities of all these 6 events is equal to 1.