Wikipedia (i/?w?kpi?di?/ or i/?w?ki?pi?di?/ wik-i-pee-dee-?) is a collaboratively edited, multilingual, free Internet encyclopedia supported by the non-profit Wikimedia Foundation. Its 24 million articles, over 4.1 million in the English Wikipedia alone, are written collaboratively by volunteers around the world. Almost all of its articles can be edited by anyone with access to the site,[4] and it has about 100,000 active contributors.[5][6] As of February 2013, there are editions of Wikipedia in 285 languages. It has become the largest and most popular general reference work on the Internet,[7][8][9][10][11] ranking sixth globally among all websites on Alexa and having an estimated 365 million readers worldwide.[7][12] Wikipedia was launched on January 15, 2001, by Jimmy Wales and Larry Sanger.[13] Sanger coined the name Wikipedia,[14] which is a portmanteau of wiki (a type of collaborative website, from the Hawaiian word wiki, meaning "quick")[15] and encyclopedia. Wikipedia's departure from the expert-driven style of encyclopedia building and the presence of a large body of unacademic content have received extensive attention in print media. In 2006, Time magazine recognized Wikipedia's participation in the rapid growth of online collaboration and interaction by millions of people around the world, in addition to YouTube, MySpace, and Facebook.[16] Wikipedia has also been praised as a news source due to articles related to breaking news often being rapidly updated.[17][18][19] The open nature of Wikipedia has led to various concerns, such as the quality of writing,[20] the amount of vandalism[21][22] and the accuracy of information. Some articles contain unverified or inconsistent information,[23] though a 2005 investigation in Nature showed that the science articles they compared came close to the level of accuracy of Encyclop?dia Britannica an

had a similar rate of "serious errors".[24] Britannica replied that the study's methodology and conclusions were flawed,[25] but Nature reacted to this refutation with both a formal response and a point-by-point rebuttal of Britannica's main objections.Editing In April 2009, the Wikimedia Foundation conducted a Wikipedia usability study, questioning users about the editing mechanism.[28] In a departure from the style of traditional encyclopedias, Wikipedia is largely open to editing. This means that, with the exception of particularly sensitive and/or vandalism-prone pages that are "protected" to some degree from editing,[29] the reader of an article can edit the text without needing approval, doing so anonymously or with a registered account. Different language editions modify this policy; for example, only registered users may create a new article in the English edition.[30] No article is considered to be owned by its creator or any other editor, nor is it vetted by any recognized authority. Instead, editors are supposed to agree on the content and structure of articles by consensus.[31] By default, an edit to an article becomes available immediately, prior to any review. As such, an article may contain inaccuracies, ideological biases, or even patent nonsense, until or unless another editor corrects the problem. Different language editions, each under separate administrative control, are free to modify this policy. For example, the German Wikipedia maintains "stable versions" of articles,[32] which have passed certain reviews. Following the protracted trials and community discussion, the "pending changes" system was introduced to English Wikipedia in December 2012.[33] Under this system, new users' edits to certain controversial or vandalism-prone articles would be "subject to review from an established Wikipedia editor before publication".