Two events are called not mutually exclusive if they have al least one outcome common between them. If the two events and are not mutually exclusive events, then.  Similarly, and are not mutually exclusive events if. Thus they must have at least one common point between them. Consider a sample space:

           
            Let    and  
            Here
            Thus, i.e. exist. Here and are not mutually exclusive events. consists of outcomes which are common to both  and. As shown in the figure a Vann diagram in which  and are not mutually exclusive events. Some area under is common with. If the eventis a part of the event, then . This is shown in the figure: