Experiment - any action where the result is uncertain e.g. roll the die. Outcome - the result of a single trial of an experiment e.g. result of a die roll. Event - any subset of all possible outcomes e.g. rolling an even number A = {2, 4, 6}. Total number of outcomes in the event usually is denoted by n(A). An outcome is favorable to an event - An outcome which fulfill the conditions of an event e.g. rolling {4} is favorable to event A that is rolling an even number. S - the set of all equally likely outcomes e.g. if S = {1, 2, 3, 4, 5, 6} then n(S) = 6. A' - the complement of event A e.g. if A is rolling an even number then A' = {1, 3, 5}