An arbitrary string of characters chosen by a user or system administrator and used to authenticate the user when he attempts to log on in order to prevent unauthorised access to his account.

A favourite activity among unimaginative computer nerds and crackers is writing programs which attempt to discover passwords by using lists of commonly chosen passwords such as people's names (spelled forwards or backwards). It is recommended that to defeat such methods passwords use a mixture of upper and lower case letters or digits and avoid proper names and real words. If you have trouble remembering random strings of characters, make up an acronym like "ihGr8trmP" ("I have great trouble remembering my password").