Wikipedia:Wikipedia is a tertiary source

Initiated as a rewording of No original research's WP:PSTS section, this essay may do well as a separate guideline (showing the links between various core content policies, WP:GNG, etc).

Wikipedia is an encyclopedia and as such Wikipedia is a tertiary source.

Definitions

 * Primary source : See also primary source


 * Primary sources are very close to the origin of a particular topic, issue or situation being written about. Examples of primary sources include archeological artifacts; photographs; historical documents such as diaries, census results, video or transcripts of surveillance, public hearings, or trials; tabulated results of surveys or questionnaires; written or recorded notes of laboratory and field research, experiments or observations, published experimental results by the person(s) actually involved in the research; original philosophical works, religious scripture, administrative documents, and artistic and fictional works.


 * Any source cannot be anything but a primary source for a Wikipedia article that has that source as its main topic.


 * Secondary source : See also secondary source


 * A secondary source is at least one step removed from the described topic. Secondary sources are reports that draw on research and other references to make interpretive, analytical or synthesized claims.


 * Depending on the field, secondary sources may include textbooks, review articles, and peer-reviewed articles publishing original research.


 * Secondary sources are best used for representing significant points of view.


 * Tertiary source : See also tertiary source


 * Tertiary sources are publications such as encyclopedias or other compendia that sum up many secondary and primary sources. Many introductory textbooks may also be considered tertiary to the extent they sum up widely accepted results of large amounts of primary and secondary sources.

Wikipedia is an encyclopedia
Wikipedia's main namespace is an encyclopedia and thus a tertiary source.


 * Wikipedia is not a primary source : Wikipedia avoids describing topics that never have been described before &mdash; doing otherwise qualifies as performing original research. Unsourced eyewitness accounts or other unsourced information obtained from personal experience should not be added to articles, as this would cause Wikipedia to become a primary source for the added information (see Verifiability).
 * Wikipedia is not a secondary source : Wikipedia does not offer interpretations or analyses that deviate from previously published interpretations and analyses &mdash; doing otherwise qualifies as performing original research.
 * Wikipedia is a tertiary source : Wikipedia summarizes descriptions, interpretations and analyses that are found in secondary sources, or bases such summaries on tertiary sources. Wikipedia illustrates such summaries and descriptions with material that is as close as possible to the primary source(s) on the described topic.
 * Illustrations can enhance the quality of Wikipedia articles : Relevant illustrations in the form of direct quotes, images, plot summaries, sound files and other media are used to enhance the over-all quality of a Wikipedia article.
 * Illustrations and primary source material should not overshadow content based on secondary and tertiary sources : If a Wikipedia article is mainly composed of images, direct quotes, or other types of illustrations or primary source material, then at least some of this material should be moved to sister projects like Wikiquote, Wikisource, Commons, or such material should be given a less prominent place in the Wikipedia article, or some of this material should be removed from the article, or more content based on secondary or tertiary sources should be added to the article, or the article should be merged with the article on a related topic, etc., depending on circumstances. The reason for this limitation regarding illustrations and primary source material is that doing otherwise would turn individual Wikipedia articles into primary or secondary sources. This is partly a style recommendation, but also a no original research requirement.
 * Primary sources is a template that can be used to indicate an article relies to heavily on primary source material.


 * Wikipedia only includes topics that are covered by sufficient secondary sources : This inclusion criterion based on the no original research principle combines with,
 * Various content policies, like Verifiability (the sources also need to be reliable), Biographies of living people (excluding use of certain defamatory sources), What Wikipedia is not (excluding certain trivial sources), Neutral point of view (generally excluding sources that only represent a tiny minority view)
 * The general notability guideline and subsidiary notability guidelines precising what are sufficient sources to warrant a separate Wikipedia article on a topic