eled because of a storm or an earthquake, in that order of likelihood. This pretty much closes the event space. When considering a trial or an experiment, events are referred to as outcomes. An experiment may consist of picking up a card from a 32-card deck. One out of the 32 possible outcomes is the card being the Queen of Hearts. The event space associated In any environment, the list of possible events is generally infinite. One may then conceive of the event space as a limited set of well defined events which encompass all known possibilities at the time of the inventory. If other unknown possibilities exist, then an event category called "other" can be introduced to close the event space. 1.1 Events, event space, and probabilities with this experiment is the list of all 32 cards. Another experiment may consist in picking up two cards successively, which defines a different event space, as illustrated in Section 1.3, which concerns combined and joint events. The probability is the mathematical measure of the likelihood associated with a given event. This measure is called p(event). By definition, the measure ranges in a zero-to-one scale. Consistently with this definition, p(event) = 0 means that the event is absolutely unlikely or "impossible," and p(event) = 1 is absolutely certain. Let us not discuss here what "absolutely" or "impossible" might really mean in our physical world. As we know, such extreme notions are only relative ones! Simply defined, without purchasing a ticket, it is impossible to win the lottery! And driving 50 mph above the speed limit while passing in front of a police patrol leads to absolute certainty of getting a ticket. Let's leave alone the weak possibilities of finding by chance the winning lottery ticket on the curb, or that the police officer turns out to be an old schoolmate. That's part of the event space, too, but let's not stretch reality too far. Let us then be satisfied here with the intuitive notions that impossibility and absolute certainty do actually exist. Next, form