Alternate section title for use in header

Question

I'm TeXing a course for a teacher of mine, and he wants me to have the section titles in the headers (I use fancyhdr to achieve this). He also wants me to retain the section titles he gave me in the original (word) file.

Since some of these section titles are too long to fit in the header title, is there a way to define a shorter version that is to be used in the header?

Enabling multiple header lines would also do.

I'm using the book class.

Answer 1

Just use the optional argument of \section in addition:

\section[short title]{long title}

This works for \chapter and other headings as well.

Note, that short title would be used in the table of contents as well. This is meaningful, in my opinion.