Events A and Ā are two Sets. One consists of all events A and the the other Ā consists of all events that are not in A. Both sets have nothing common between them, hence they are disjoint .

As an example consider a collection of all positive integers. This we may identify as an Universal set. Now If all the even integers are grouped in a Set A, the remaining integers would be all odd. This Set of Odd integers would be set Ā .

Another example may be that of a set of some people consisting of both males and females. If the set of all males is termed as A, then the set of remaining females would be termed as Set Ā.

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