Redefine chapter* format

Question

How can I modify the font of the chapter* command. I essentially want to keep it the same except to make the font a little smaller. How could I do this using titlesec. Also how can I redefine the chapter* command so that I can add these sections to the table of contents.

Answer 1

You can use the numberless feature of titlesec, but you must also define a format for the numbered chapters.

\documentclass{book}
\usepackage{titlesec}

% the following emulates the standard
\titleformat{\chapter}[display]
  {\normalfont\huge\bfseries}
  {\chaptertitlename\ \thechapter}
  {20pt}
  {\Huge}
% format for numberless chapters
\titleformat{name=\chapter,numberless}[display]
 {\large\sffamily}
 {}% this argument isn't used
 {0pt}% unused
 {\managechapter}

\makeatletter
\newcommand{\managechapter}[1]{%
  #1% print the title
  \if@mainmatter
    \addcontentsline{toc}{chapter}{#1}% send to the toc
    \@mkboth{\MakeUppercase{#1}}{\MakeUppercase{#1}}% like book does usually
  \fi
}
\makeatother

\begin{document}

\frontmatter

\tableofcontents

\listoffigures

\mainmatter

\chapter*{Introduction}

\chapter{Normal chapter}

\end{document}

In the numberless format I used a very distinctive font choice, just to show the result. Notice that this also changes the format for the table of contents and the other lists.

The \if@mainmatter condition is necessary, as you don't want that the table of contents ends up listed in itself.

If you want the list of figures and similar chapters to go in the toc, add

\usepackage[nottoc]{tocbibind}