A subset of the outcomes of a process. For instance, the set of outcomes {2, 4, 6} when rolling a die is an event that one might call "rolling an even number".
Events whose probabilities add up to 1. Two events are complementary when one event occurs if and only if the other does not.
The ratio of the probability of an event to the probability of its complement; i.e., the ratio of favorable outcomes to unfavorable outcomes.
The possible results of an event. For example, when a die is rolled, the possible outcomes are 1, 2, 3, 4, 5, and 6.
A measure of the likeliness that an event will happen.
Probability = |