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:
Chapter 1. Title
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: