Washington - Just a few years ago, the word "wiki" wasn't even in most people's vocabulary. But Wikipedia - known by many as biggest encyclopaedia on the Internet - changed all that.

If you've spent much time at all searching for information on the Internet, chances are good that you've run into pages from Wikipedia. But Wikipedia itself is just one of many useful wikis online.

--- What's a wiki?

Few actually know what the word "wiki" means. Look it up in a dictionary, and you'll probably find a definition such as "a collaborative Web site the content of which can be edited by anyone who has access to it."

That definition is a good place to start, but there's more you should know. You can think of a wiki as a huge classroom board on which a room full of students can work together to compose essays on any number of topics.

Not only can the students add their own contributions to the board, but they can also change sections that other students have written when those sections contain errors or inaccuracies.

What's more, as other students walk in and read what's been written, they, too, can add to the essays, make changes to them, or create new ones altogether. This process can conceivably continue without end, and in this sense a wiki is very much always a work in progress.

A traditional wiki is policed by no one except the community. Users can make changes or additions at will, which might lead one to believe that the content of wikis would be highly unreliable - even chaotic. Interestingly enough, that's rarely the case.

The wiki often ends up being revered by the community, a symbol of community effort, and contributors generally take pride in ensuring that its contents are accurate and not violated.

Today's most established and well-respected wikis on the Internet, however, are not quite the free-for-all that they could be. The major wikis online have volunteer editors assigned to particular sections or topics, and any new content added is either accepted or rejected by these editors before or soon after the new content appears. Anyone, though, can generally be a contributor to a wiki - and that means you, too.

Wikipedia (http://www.wikipedia.org) is the Internet's shining example of all that a wiki can be. Wikipedia contains over 7 million articles in more than 200 languages, and even a brief look through this impressive site reveals that the articles are generally of high quality.

The Internet-using public clearly agrees. A recent study from U. S.-based Pew Internet showed that 50 per cent of Internet users consult the massive online encyclopaedia on a regular basis. The fact that all of the content of Wikipedia is user-generated does not seem to matter to those who use it.

Critics, however, are quick to point out that the information in Wikipedia, because it can contain information that has not been vetted in the traditional sense, should not be seen as authoritative.

Clearly, though, Wikipedia has shown that the wiki concept works, and lots of other wikis are now following in its footsteps.

--- Wiki proliferation

The same folks that run Wikipedia also run several other useful Wikis, and as you might expect, they're all interesting and helpful. Wiktionary (http://www.wiktionary.org) is a wiki version of a dictionary. It contains definitions in dozens of languages and provides audio clips that aid in pronunciation.

Synonyms and etymologies are included, as well, and you can explore related words instantly by clicking links. A "translations" section for each defined word even allows you to explore the word's equivalent word in other languages.

Wikibooks (http://www.wikibooks.org) is perhaps even more ambitious than Wikipedia. Instead of providing collaborative articles on particular topics, Wikibooks offers free educational textbooks on a wide range of topics - everything from organic chemistry to physics.

Proponents of the wiki book model argue that wikis themselves are the perfect vehicle for maintaining textbooks. The content of traditional textbooks, they argue, is often outdated by the time the books reach readers. Since wikis can be updated continuously, the content stays current and relevant.

Wikinews (http://en.wikinews.org) is a news site by and for the readers. As with wikis, anyone can contribute to or edit the content presented, but all participants must agree to write from a neutral point of view and with a global audience in mind.

If your work gets edited or removed, it will probably be because you did not follow the news site's guidelines, which are clearly laid out for those who wish to be part of this news service.

Wikitravel (http://wikitravel.org) merges the concept of the wiki with the popularity of the travel guide. The result: up-to-date travel information on just about any destination around the world, typically written by people who have in-depth knowledge of the places and their inhabitants.

This guide does far more than your average travel book, as there are no restrictions on topics covered or the amount of space devoted to descriptions. So you'll find background information, detailed maps, tips on the best restaurants, and much more.

These are just a few of the hundreds of wikis now online. The wiki concept is now a proven success, so projects encompassing many subjects and regions are now online.

To get some idea of the breadth of material available on wikis, your best bet is to visit a wiki directory such as Everything Wiki
(http://wiki.wetpaint.com/page/Wiki+Directory? t=anon) or Wiki Spot (http://wikispot.org/Wiki_Directory). Bring some time, though: it's easy to get lost exploring the wide world of wikis. (dpa)