Why do exceptions usually have the suffix 'Exception' in the class name?

Question

It seems to me that it is rendundant information as the usage of the class will make it apparent that it is an exception. Furthermore, in PHP, the class must extend the Exception class so it will be apparent that it is an exception when looking at the class on its own.

Despite this, developers usually apply the suffix 'Exception'. Why is this?

Answer 1

Imagine two classes, InvalidIndex and InvalidIndexException. A class named InvalidIndex might be completely valid (e.g. to invalidate database indexes or something like that) and not related to an exception. If you now had an exception for invalid array indices you'd have a naming problem. By suffixing exception classes with Exception, you avoid name conflicts like that.

Answer 2

I know of no binding rule for this, but I guess it simply makes sense.

class FileNotFound

could mean a number of things, while

class FileNotFoundException

makes the Exception character very clear.