The encyclopedia proper is the main namespace and contains all of Wikipedia's encyclopedia articles. All of the other namespaces have prefixes, which must be included (followed by a colon) at the beginning of links to pages in those namespaces in order for those links to work. Otherwise, the links will point to the main namespace, which has no prefix.

Currently, Wikipedia has 30 namespaces: 14 subject namespaces, 14 corresponding talk namespaces, and 2 virtual namespaces.

The namespaces (by prefix) are:

1. Main/Article (no prefix), Talk:
2. User:, User talk:
3. Wikipedia:, Wikipedia talk:
4. File:, File talk:
5. MediaWiki:, MediaWiki talk:
6. Template:, Template talk:
7. Help:, Help talk:
8. Category:, Category talk:
9. Portal:, Portal talk:
10. Book:, Book talk:
11. Draft:, Draft talk:
12. Education Program:, Education Program talk:
13. Timedtext:, Timedtext talk:
14. Module:, Module talk:

The virtual namespaces are:

1. Media:
2. Special:

In any given namespace there can only be one page with a particular name.