(As the categorisation concept originated in Wikipedia, readers may benefit by skimming a page such as Wikipedia:Wikipedia:Categorisation_FAQ)

This page is for detailed reasons and recommendations about why we have categories and how to make the best use of them, including ways of arranging articles and subcategories in other than strict alphabetical order.


Categories (introduced to Wikipedia in 2004 and since available in all sites using MediaWiki software) are an excellent way of linking related pages and automatically listing them in alphabetical order. Spin-off benefits include the ability to see if there are gaps in a subject or inconsistencies in naming or grouping.

Every category except the top one should be a subcategory of at least one category, but will often be suitable for two or more; for example, "Category:Engineers organisations in Australia" could be in both "Category:Engineers organisations" and "Category:Organisations based in Australia".

Similarly, every article should be in at least one category but will very often be suitable for two or more.

Names of categories[]

  1. Category and article names should:
    1. not start with "Engineer..." unless it is part of a formal name - in this respect we differ from Wikipedia because most of our categories will be specifically about Engineering, and their alphabetical listing would be unbalanced and hard to use if most were under "E" but similar categories were under the subject name
    2. otherwise match those of Wikipedia as closely as convenient because that leads to considerable time-saving and helps with cross-referencing (for example, in the use of Template:alsoWP)
  2. Category names should be plural if any of the contents can be counted
  3. Use the MediaWiki standard "sentence case" (where most words do not have a capital letter)

Overlapping subject-matter[]

If two categories have overlapping subject-matter with each having some that's not in the other (eg Category:Engineers and Category:United States or Category:Science), they can each include (in the text portion) a link to the other (which can be quickly and neatly effected by using Template:seealso listing one or more related categories), but neither should be a subcategory of the other. Circularity, nonsensical paths, and endless loops can result.

With articles, more freedom is allowed: an article can be in a category if a large part of its subject-matter belongs in the category even if some doesn't. For example, "United States" can be in Category:North America even though one of its states is far off in the Pacific Ocean.

Fiddling with the listing order[]

Some categories are best if articles are arranged by some order other than the actual article name. Lists of people, for example. To list in a category under something other than the article name (eg a surname), add a pipe and the desired alternative just before the final brackets, eg [[category:engineers|Stephenson, George]].

When an article has the same name as a category (or almost), it should be listed at the top of the category by adding "|*" before the end brackets of the category link. Similarly with an "Engineering" subcategory of a "disciplines" category, so that it lists before other disciplines.

How you can help improve the categorisation[]

  1. Use the Talk pages to suggest categories that have not yet been used
  2. Browse the "special" pages to find pages that are not in categories (and put them in one or two):