Any part of the sample space is called an even of a probability. An event may contain one or more than one outcomes. When an event consists of a single outcome (sample points), it is called a simple event. An event which has two or more outcomes is called a compound event. The sample points contained in an event are written within brackets . If we consider a single face when a die is thrown, it is a simple event. Getting on a die when thrown is called the occurrences of a simple event. If the event is any prime number on the die, the event consists of the points . It is a compound event and consists of three simple events which are and . When two dice are thrown, the pair is a single outcome in the sample space and is therefore a simple event. The event “total is ” consist of two outcomes that is and. Thus “total is ” is a compound event.

If a random experiment can produced sample points, it has simple events. Throw of a single die has simple events and a throw of two dice produced simple events. The empty set is also an event but it is not a simple event. The sample space is a compound event is called a certain event.