Wikipedia:Article namespace.html

Namespace
Main namespace
Wikipedia namespace
Help namespace
User namespace
Category namespace
Image namespace
MediaWiki namespace (help)
Template namespace
Special namespace
Media namespace
Portal namespace
Table namespace

The main namespace or article namespace is the namespace of Wikipedia that contains the encyclopedia proper (see Special:Allpages). It is the default namespace and does not use a prefix in article page names.

This namespace contains Wikipedia articles.

Not all pages in the article namespace are considered to be articles; the most notable exceptions are:

the Main Page;
for wiki-statistical purposes, some extremely short and simple pages are not counted as articles. The criteria varied over time.
thousands of disambiguation pages which are used to resolve naming conflicts;
many millions of redirect pages which are used to re-route one page to another page.
Many wikipedia lists are navigation tools, rather than encyclopedic articles per se. Annotated lists, especially the ones voted to be "featured lists", such as the List of ISS spacewalks, deserve to be treated as encyclopedic articles.

Talk pages for the articles belong to the "Talk" namespace, i.e., the pagenames start with the prefix "Talk:". For example "Talk:Wikipedia" is the talk page for the "Wikipedia" article.