The basic terms used in defining probability are:
2.1.1 Trial and event:
If we take an experiment in which the experiment is repeated under essentially same conditions, the outcome won’t be unique but may result in any of the possible outcomes. The experiment is known as a trial and the outcomes are known as events or cases.
2.1.2 Exhaustive events:
The all possible outcomes of any experiment are known as the exhaustive events.
2.1.3 Favourable events or cases:
The number of events favourable to an event in an experiment is the number of outcomes which entail the happening of the event.
2.1.4 Mutually exclusive events:
The happening of any one of them precludes the happening of all the other events that is if no two or more of them can happen simultaneously in the same trial.
2.1.5 Equally likely events:
Outcomes of an experiment is said to be equally likely if taking into consideration of all the relevant evidences there is no reason to expect one in preference to the others.
2.1.6 Independent events:
Several events are said to be independent if the happening of an event is not affected by the supplementary knowledge concerning the occurrence of any number of the remaining events.