To delete a wiki page, edit the page, select (highlight) all text in the edit textarea, and replace it with the single word
delete
It is a good idea to add a comment to the summary field
explaining why you deleted the page. (The field summary is usually found
just below the edit textarea).
On saving the change the page is deleted. As an added safety feature, the deleted page still exists on the server (with a timestamp) and can be restored to the former page by the wiki administrator.
If you suspect that a page has been deleted but aren't sure, have a look at the wikigroup's RecentChanges. Erasing a page counts as editing the page, and the activity is recorded there and on Site.AllRecentChanges.
The default word used for page deletion ("delete") can be changed in config.php by setting the variable $DeleteKeyPattern (see Edit Variables).
If there is a danger of malicious page deletion it may be a good idea to change the delete word to something more obscure.
There is also a recipe for creating a separate delete action at Cookbook:DeleteAction.
The deleted pages are retained in the same wiki.d directory in which they were created.
They are renamed with an extension of ,del-123456789 where 123456789 is a unique number (timestamp).
A wiki administrator may log into the server via FTP or SSH and periodically remove these files.
One way to remove the files is to delete them.
If you have shell access, you could use different commands, for example, go into the wiki.d directory and type one of these lines:
rm -f *,del-* find . -name '*,del-*' -delete
Alternatively, the Cookbook:CleanUp recipe can purge those unused files. See also BackupAndRestore.
How is a Wiki Group deleted?
An admin can remove the group pages from wiki.d/. Note that a wiki page may also have related uploads.
Fully deleting a group via the wiki isn't possible, since a delete counts as an "update" which causes the Recent Changes page to be re-created.
It is possible to modify the site's configuration to allow deletion of the group's RecentChanges page -- see Cookbook:RecentChangesDeletion.
How is a Category deleted?
To delete a category, delete all the [[!Category]] references from all pages where they occur, then delete the category page as explained above.