Wikipedia (Listeni/ˌwɪkɨˈpiːdiə/ or Listeni/ˌwɪkiˈpiːdiə/ wik-i-pee-dee-ə) is a free-access, free content Internet encyclopedia, supported and hosted by the non-profit Wikimedia Foundation. Anyone who can access the site[5] can edit almost any of its articles. Wikipedia is the sixth-most popular website[4] and constitutes the Internet's largest and most popular general reference work.[6][7][8] As of February 2014, it had 18 billion page views and nearly 500 million unique visitors each month.[9] Wikipedia has more than 22 million accounts, out of which there were over 73,000 active editors globally as of May 2014.[2]
Jimmy Wales and Larry Sanger launched Wikipedia on January 15, 2001. Sanger[10] coined its name,[11] a portmanteau of wiki (from the Hawaiian word for "quick")[12] and encyclopedia. Although Wikipedia's content was initially only in English, it quickly became multilingual, through the launch of versions in different languages. All versions of Wikipedia are similar, but important differences exist in content and in editing practices. The English Wikipedia is now one of more than 200 Wikipedias, but remains the largest one, with over 4.6 million articles.
A 2005 survey of Wikipedia published in Nature based on a comparison of 42 science articles with Encyclopædia Britannica found that Wikipedia's level of accuracy approached Encyclopædia Britannica ' s, and both had similar low rates of "serious errors".[13] Critics have stated that Wikipedia exhibits systemic bias, and that its group dynamics hinder its goals. Most academics, historians, teachers and journalists reject Wikipedia as a reliable source of information for being a mixture of truths, half truths, and some falsehoods,[14] and that as a resource about controversial topics, Wikipedia is notoriously subject to manipulation and spin.[15] Wikipedia's Consensus and Undue Weight policies have been repeatedly criticised by prominent scholarly sources for undermining freedom of thought and leading to false beliefs based on incomplete information.[16][17][18][19] The casual reader is not aware of these controversial policies because he/she assumes Wikipedia has no restrictions on freedom of information.[20] The Academic Integrity at MIT handbook for students at Massachusetts Institute of Technology states: "Wikipedia is Not a Reliable Academic Source: The bibliography published at the end of the Wikipedia entry may point you to potential sources. However, do not assume that these sources are reliable – use the same criteria to judge them as you would any other source. Do not consider the Wikipedia bibliography as a replacement for your own research."[21]
Contents [hide]
1 Openness
1.1 Restrictions
1.2 Review of changes
1.3 Vandalism
2 Policies and laws
2.1 Content policies
3 Governance
3.1 Administrators
3.2 Dispute resolution
4 Community
4.1 Diversity
5 Language editions
6 History
7 Critical reception
7.1 Accuracy of content
7.2 Quality of writing
7.3 Coverage of topics and systemic bias
7.4 Explicit content
7.5 Privacy
7.6 Wikipedia conflicts in the media
8 Operation
8.1 Wikimedia Foundation and the Wikimedia chapters
8.2 Software operations and support
8.3 Automated editing
8.4 Wikiprojects and assessment of importance
8.5 Hardware operations and support
8.6 Internal research and operational development
8.7 Internal news publications
9 Access to content
9.1 Content licensing
9.2 Methods of access
10 Impact
10.1 Readership
10.2 Cultural significance
10.3 Sister projects – Wikimedia
10.4 Publishing
10.5 Scientific use
11 Related projects
12 See also
13 References
13.1 Notes
13.2 Further reading
14 External links
Openness

Differences between versions of an article are highlighted as shown.
Unlike traditional encyclopedias, Wikipedia follows the procrastination principle[clarify] regarding the security of its content;[22] it started almost entirely open—anyone could create articles, and any Wikipedia article