### My section title is too wide for the page header

By default, LaTeX sectioning commands make the chapter or section title available for use by page headers and the like. Page headers operate in a rather constrained area, and it's common for titles too be too big to fit: the LaTeX sectioning commands therefore take an optional argument:

    \section[short title]{full title}

If the <short title> is present, it is used both for the table of contents and for the page heading: the usual answer to people who complain about the size of the title that's gone in to the running head, is to suggest that they the optional argument.

However, using the same text for the table of contents as for the running head may also be unsatisfactory: if your chapter titles are seriously long (like those of a Victorian novel), a valid and rational scheme is to have a shortened table of contents entry, and a really terse entry in the running head.

In fact, the sectioning commands use 'mark' commands to pass information to the page headers. For example, `\chapter` uses `\chaptermark`, `\section` uses `\sectionmark`, and so on. With this knowledge, one can achieve a three-layer structure for chapters:

    \chapter[middling version]{verbose version}
    \chaptermark{terse version}

which should supply the needs of every taste.

Chapters, however, have it easy: hardly any book design puts a page header on a chapter start page. In the case of sections, one has typically to take account of the nature of the `\*mark` commands: the thing that goes in the heading is the first mark on the page (or, failing any mark, the last mark on any previous page). As a result the recipe for sections is more tiresome:

    \section[middling version]{verbose version%
                    \sectionmark{terse version}}
    \sectionmark{terse version}

(the first `\sectionmark` deals with the header of the page the `\section` command falls on, and the second deal with subsequent pages; note that here, you need the optional argument to `\section`, even if "middling version" is in fact the same text as "long version".)

A similar arrangement is necessary even for chapters if the class you're using is odd enough that it puts a page header on a chapter's opening page.

Note that the titlesec package manages the running heads in a completely different fashion; users of that package should refer to the documentation.

`titlesec.sty`
  macros/latex/contrib/supported/titlesec.tar.gz