Wikipedia is a free-access, free-content Internet encyclopedia, supported and hosted by the non-profit Wikimedia Foundation. Those who can access the site can edit most of its articles. Wikipedia is ranked among the ten most popular websites, and constitutes the Internet’s largest and most popular general reference work.
Jimmy Wales and Larry Sanger launched Wikipedia on January 15, 2001. Sanger coined its name, a portmanteau of wiki and encyclopedia. Initially only in English, Wikipedia quickly became multilingual as it developed similar versions in other languages, which differ in content and in editing practices. The English Wikipedia is now one of 291 Wikipedia editions and is the largest with 5,056,792 articles (having reached 5,000,000 articles in November 2015). There is a grand total, including all Wikipedias, of over 38 million articles in over 250 different languages. As of February 2014, it had 18 billion page views and nearly 500 million unique visitors each month.
A peer review of 42 science articles found in both Encyclopædia Britannica and Wikipedia was published in Nature in 2005, and found that Wikipedia’s level of accuracy approached Encyclopedia Britannica ’s.