Wikipedia:Categories

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.

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.

After you have determined an appropriate category name and know its parent category, you are ready to create the new category. To create a category, first add an article to that category. Do this by editing the article page. At the bottom, but before the (if any are present), add the name of the new category, (e.g.: [[Category:New category name]] ), and save your edit. The as-yet-undefined category name will now appear as a red link in the article's category list at the bottom of the page.

Next, to create the category, click on that red link, which brings you back into the editor. Adding this new category into the appropriate parent category is much the same as with an article: at the bottom, simply add the parent category (e.g.: [[Category:Parent category name]] ).

Sometimes, a common-sense guess based on the title of the category isn't enough to figure out whether a page should be listed in the category. So, rather than leave the text of a category page empty (containing only parent category declarations), it is helpful – to both readers and editors – to include a description of the category, indicating what pages it should contain, how they should be subcategorized, and so on.

In such cases, the desired contents of the category should be described on the category page, similar to how the list selection criteria are described in a stand-alone list. The category description should make direct statements about the criteria by which pages should be selected for inclusion in (or exclusion from) the category. This description, not the category's name, defines the proper content of the category. Do not leave future editors to guess about what or who should be included from the title of the category. Even if the selection criteria might seem obvious to you, an explicit standard is helpful to others, especially if they are less familiar with the subject.

Various templates have been developed to make it easier to produce category descriptions; see Category namespace templates. There are hatnote templates including {{}} and {{}}; others are listed at .

...
Wikipedia