Wikipedia:Copying within Wikipedia

Wikipedia's licensing requires that attribution be given to all users involved in creating and altering the content of a page. Wikipedia's page history functionality lists all edits made to a page and all users who made these changes, but it cannot, however, in itself determine where text originally came from. Because of this, copying content from another page within Wikipedia requires supplementary attribution to indicate it. At minimum, this means providing an edit summary at the destination page – that is, the page into which the material is copied – stating that content was copied, together with a link to the source (copied-from) page, e.g. Copied content from [[<page name>]]; see that page's history for attribution. It is good practice, especially if copying is extensive, to make a note in an edit summary at the source page as well. Content reusers should also consider leaving notes at the talk pages of both source and destination.

Copying and translating information from a Wikimedia project other than the English Wikipedia is usually possible, since all Wikimedia projects use the same or compatible licensing for most of their content. The edit summary should provide either a link to the original source or a list of all contributors. Additionally, there are templates that can and should be used for attribution. See § Copying from other Wikimedia projects for more info.

Attribution is required for copyright

Contributors to Wikipedia are not asked to surrender their copyright to the material they contribute. Instead, they are required to co-license their contributions under the copyleft licenses Creative Commons Attribution-ShareAlike 3.0 Unported License (CC BY-SA) and GNU Free Documentation License (GFDL). Both of these licenses allow reuse and modification, but reserve the right to attribution.

The CC BY-SA, section 4(c), states that:

You must ... provide ... the name of the Original Author (or pseudonym, if applicable) ... and ... in the case of an Adaptation, a credit identifying the use of the Work in the Adaptation (e.g., "French translation of the Work by Original Author," or "Screenplay based on original Work by Original Author"). The credit required by this Section 4(c) may be implemented in any reasonable manner; provided, however, that in the case of a Adaptation or Collection, at a minimum such credit will appear, if a credit for all contributing authors of the Adaptation or Collection appears, then as part of these credits and in a manner at least as prominent as the credits for the other contributing authors.

The GFDL, section 4-I, states that:

... you must ... Preserve the section Entitled "History", Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page.

The Wikimedia Foundation's Terms of Use are clear that attribution will be supplied:

in any of the following fashions: a) through a hyperlink (where possible) or URL to the article or articles you contributed to, b) through a hyperlink (where possible) or URL to an alternative, stable online copy which is freely accessible, which conforms with the license, and which provides credit to the authors in a manner equivalent to the credit given on this website, or c) through a list of all authors. (Any list of authors may be filtered to exclude very small or irrelevant contributions.)

If material is used without attribution, it violates the licensing terms under which it has been provided, which in turn violates the Reusers' rights and obligations clause of Wikipedia's copyrights policy.