You can define an abbreviation for commonly used words or phrases. For example, if you type:

:ab www World Wide Web

and then press <Enter>, this sets the abbreviation. As soon as you type the abbreviation in text and move the cursor to the next space after www, the abbreviation is expanded into the associated phrase. The abbreviation function is case-sensitive. An abbreviation lasts for the duration of a vi session. For information about how to set up a file with frequently used editing options, see Setting up an editing options command file.

If you want to get rid of an abbreviation that has been set, use the :una (unabbreviate) command. For example, type:

:una www

to get rid of the abbreviation.