A wiki (sometimes spelled "Wiki") is a server program that allows users to collaborate in forming the content of a Web site. The term comes from the word "wikiwiki," which means "fast" in the Hawaiian language.

A wiki provides a simplified interface. It is not necessary to know HTML. At any time, contributors can review the history of the page they are working on or preview the Web page before publishing it. 

A wiki Web site operates on a principle of collaborative trust. The simplest wiki programs allow users to create and edit content. More advanced wikis have a management component that allow a designated person to accept or reject changes. The best known example of a wiki Web site is Wikipedia.