The prefix 'pre' is a three-letter word that means 'prior to.' It is often used to describe something that happened before a certain event or time. For example, 'pre-war' would refer to something that happened before a war began. Similarly, 'pre-election' would refer to something that happened before an election. The prefix 'pre' can also be used to describe something that is done in preparation for something else, such as 'pre-planning' or 'pre-arranged.'