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A category scheme is a way to index Wikipedia articles. Many category schemes are possible, and there is no scheme that is clearly the best. Furthermore, many of these categories are incomplete — some categorise only the broadest topics, others don't even get that far. See the discussion page for other proposed category schemes. The topmost levels are included below. Click on entries to see successively lower levels in each scheme.

The Wikipedia category system is designed to index articles by subject parentage, where the index is automatically generated from mark-up information (category tags) placed (at the end of) in each article. The top of the category system hierarchy can be accessed via Wikipedia:Browse, Category:Categories, and Category:Fundamental.

Pros: centralized
Cons: cumbersome (categories can't be edited directly), awkward (category listings are not present at the point of data-entry forcing user to remember category names on his own or guess), it's easier to navigate down the tree than up it, administrative category system hard to find (especially for newbies).

See also:

Wikipedia:Category for a quick introduction to categories.
Wikipedia:categorization for a detailed manual including instructions and policies about creating and applying categories, and about categories outside article space.
Wikipedia:Categorisation FAQ for everything you ever wanted to know about categories.
Wikipedia administration for an index of topics about Wikipedia, how to use it, and how it is managed. Includes help articles, policy articles, voting pages, and administrator-related articles.
  • Wikipedia Almanac -- includes lists of terms, in which many of the tems are live links to articles. Even though the lists presented contain many terms which are not article titles, the topic coverage is so comprehensive as to make this the most complete organized indexing system of Wikipedia. It is also referred to as the Wikipedia Almanac.
  • Wikipedia:Concise -- Wikipedia version of a concise encyclopedia. Under construction. Planned to be a list of 15,000 to 20,000 essential topics. Looking for volunteers for gathering essential lists, sorting, and purging duplicate entries.
  • List of basic topic lists -- includes short lists of key topics on major subjects. It serves as a good condensed table of contents to Wikipedia.
  • List of topic lists -- intended to be a comprehensive list of article lists, arranged by subject. Under construction.
  • Wikipedia:Browse by overview -- list of major articles, called "overview articles": articles with the same names as portals and major categories.
  • Wikipedia:Dewey Decimal System -- a work-in-progress to organize all Wikipedia article titles according to the Dewey Decimal System of library cataloging.
  • List of academic disciplines -- Wikipedia arranged like a college course curriculum.
  • Category:Topic lists - the list of lists, in the category system.

Alphabetic lists އުނިއިތުރު ގެންނަވާ

Glossaries (topic lists with definitions included) އުނިއިތުރު ގެންނަވާ

Reference tables އުނިއިތުރު ގެންނަވާ

Timelines އުނިއިތުރު ގެންނަވާ

(articles organized chronologically)

Portals are theme pages. Most feature articles, a picture or two, and news items. Many also contain topic lists, and some contain lists of categories.

(indices of pages for Wikipedia editors)

Category schemes — what will eventually be a listing of various schemes used for categorization outside of wikipedia. hint, hint.