Chapters

If the chapter-signifier (i.e., prefix) is set, the value of this attribute is automatically added to the beginning of chapter titles in a book when the sectnums attribute is also set. The signifier is offset from the auto-generated chapter number by a space. For example, the chapter title may appear in the output document as follows:

A chapter is defined as a level 1 section without a block style when the doctype type is book. You can modify the signifier by defining the chapter-signifier attribute in the header of your book.

To remove the prefix, unset the chapter-signifier attribute in the document header: