This page contains guidance on the proper use of the categorization function in Wikipedia. For information on the mechanics of the function, category syntax, etc., see Help:Category. For quick answers, see the Categorization FAQ. For proposals to delete, merge, or rename categories, follow the instructions at Categories for discussion. Please use it before undertaking any complicated re-categorization of existing categories or mass creation of new categories.

The central goal of the category system is to provide navigational links to Wikipedia pages in a hierarchy of categories which readers, knowing essential—defining—characteristics of a topic, can browse and quickly find sets of pages on topics that are defined by those characteristics.

Categories are not the only means of enabling users to browse sets of related pages. Other tools which may be used instead of or alongside categories in particular instances include lists and navigation boxes. For a comparison of these techniques, see Categories, lists and navigation templates.

Naming conventions

When naming a category, one should be particularly careful and choose its name accurately. Moving non-conventionally categorized pages to another category name (see ) imposes an additional overhead – an edit for each article and subcategory.

General conventions

  • Standard article naming conventions apply; in particular, do not capitalize regular nouns except when they come at the beginning of the title.
  • Names of topic categories should be singular, normally corresponding to the name of a Wikipedia article. Examples: "Law", "France", "George W. Bush".
  • Names of set categories should be plural. Examples: "Writers", "Villages in Poland".
  • Avoid abbreviations. Example: "Category:Military equipment of World War II", not ":Category:Military equipment of WW2". However, abbreviations that have become the official or generally used name (such as NATO) should be used where there are no other conflicts.
  • Don't write the category structure in names. Example: "Monarchs", not "People - Monarchs".
  • Choose category names that can stand alone, independent of the way a category is connected to other categories. Example: "Geography terminology stubs", not "Terminology" (a subcategory of "Geography stubs").
  • As with lists, avoid descriptive adjectives such as famous, important, or notable in category titles.
  • Particularly for technical subjects, use words and phrases which exist in reliable sources, so that those sources may be used to support inclusion of articles.

Special conventions

  • Note that in many instances a topic category and a set category have similar names, the topic category being singular and the set category plural. For example, Opera is a topic category (containing all articles relating to the topic), while Operas is a set category (containing articles about specific operas). Be careful to choose the right one when categorizing articles.
  • If there are a lot of lists in a particular subject area, it may be useful to have a category to hold them, called something like "Category:Lists of countries". These categories should only contain list pages (for example "List of Soviet Republics", "List of countries by population"). When placing pages in such a category, use a sort key that excludes the phrase "List of" (otherwise all lists would appear under "L"). See also Category:Lists.
  • All WikiProject categories should have "WikiProject" (or "WikiProjects") as part of the name. Note that this does not apply to the names of categories that projects might create for the use of assessments. In these cases, the advice given in Project Categories, which conforms to Category:Wikipedia 1.0 assessments is advised, though not mandatory.
  • Categories used for Wikipedia administration are prefixed with the word "Wikipedia" (no colon) if this is needed to prevent confusion with content categories. For example, Category:Inactive project pages (where no confusion is likely), but Category:Wikipedia tools (as distinct from the content category Tools).
  • Naming guidelines for sub-categories of Category:Stub categories are listed at Wikipedia:WikiProject Stub sorting/Naming guidelines#Categories.
  • For categorization in userspace, see Wikipedia:Categorization#User namespace and Wikipedia:User categories#Naming conventions.
  • For geographical photo requests, the category name should be 'Wikipedia requested photographs in xxx' as in [[Category:Wikipedia requested photographs in England]]. Wikiprojects desiring to keep track of articles needing photos should use 'xxxx articles needing photos' as in [[Category:England articles needing photos]] and [[Category:England articles needing images]] (for photos, maps, drawings, etc.)
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