In our study of probability, we will be interested not only in the individual outcomes of but also in various collections of outcomes from .
event
An event is any collection (subset) of outcomes contained in the sample space .
simple vs compound
An event is simple if it consists of exactly one outcome and compound if it consists of more than one outcome.
occur
When an experiment is performed, a particular event is said to occur if the resulting experimental outcome is contained in .
In general, exactly one simple event will occur, but many compound events will occur simultaneously.