web -based encyclopedia project , written collaboratively and currently administered by the Wikimedia Foundation, a non-profit organization whose mission is "to empower and engage people around the world to collect and develop educational content under a free license or in the domain , and to disseminate it effectively and globally."

As part of several projects maintained by Wikimedia, the more than 30 million articles (in Portuguese) found on Wikipedia today were written collaboratively by numerous volunteers around the world; and almost all entries on the site can also be edited by anyone with internet access and the website http://www.wikipedia.org.

In October 2013, there were active editions of Wikipedia in 277 languages.

Wikipedia was launched on January 15, 2001 by Jimmy Wales and Larry Sanger and has become the largest and most popular general reference work on the Internet, ranking around seventh among all Alexa websites and having approximately 365 million readers.

Wikipedia is a research for students and has influenced the work of advertisers, educators, sociologists, and journalists, who use its material even if they don't always cite their sources.

The name Wikipedia was created by Larry Sanger and is a combination of wiki (a technology for creating collaborative websites, from the Hawaiian word wiki, meaning "fast") and encyclopedia. The word "Wikipedia" is a Portuguese adaptation of the original English form, a fusion of the two words spelling "Wiki" + "pedia".

In Portuguese, the prefix "Wiki," combined with the suffix "enciclopédia," gains an acute diacritical accent on the "e" to conform to Portuguese grammar. Wikipedia departs from the traditional style of encyclopedia construction and features a large amount of non-academic content.

When Time magazine recognized "You" as Person of the Year in 2006, due to the accelerated success of online collaboration and the interaction of millions of users around the world, it cited Wikipedia as one of several examples of Web 2.0 , along with YouTube, MySpace, and Facebook.

Some have noted the importance of Wikipedia, not only as an encyclopedic reference, but also as a frequently updated news resource because of the speed at which articles about recent events appear.

Students have been instructed to write Wikipedia articles as an exercise in clearly and succinctly explaining difficult concepts to a non-initiated audience. Although Wikipedia's policies strongly advocate verifiability and a neutral viewpoint, its critics accuse it of systemic bias and inconsistencies (including the excessive weight given to popular culture) and claim that it favors consensus over credentials in its editorial processes.

Its reliability and accuracy are also subject to criticism. Other criticisms point to its susceptibility to vandalism and the addition of false or unverified information

A 2005 study in the journal Nature showed that the scientific articles they compared came close to the level of accuracy of the Encyclopædia Britannica and had a similar rate of "serious errors".

Another 2011 survey conducted by ForeSee Results and published by CNET showed that, on a satisfaction scale of 0 to 100, internet users gave Wikipedia a score of 78, a higher result than other established sites such as YouTube and Facebook.