Use hyphenation command with underscores

Question

I have words in my text that contains underscores and that exceeds the boundaries of the page

the word is typed in the text as

FOS\_SOCIAL\_SCIENCE

I want the word to be able to hyphenate at the underscore boundaries.

I have tried:

\hyphenation{FOS-\_-NA-TU-RAL-\_-SCIEN-CE}

but pdfLatex return the following error

Improper \hyphenation will be flushed. \hyphenation{FOS-_

I don't want to use the underscore package due to incompatibilities

I also tried

\renewcommand{\_}{%
    \textunderscore\nobreak\hspace{0pt}%
}

which doesn't work: compile without errors but the word is not hyphenated

I also tried:

\def\_{\_\allowbreak\hspace{0pt}}

which does not compile. The error message is:

TeX capacity exceeded, sorry [input stack size=5000]. \item[FOS_NATURAL_SCIENCE]

Answer 1

Why do you use \nobreak if you want something to break? Without it it works as expected:

\documentclass{article}

\textwidth=1mm
\begin{document}
FOS\_SOCIAL\_SCIENCE   

\renewcommand{\_}{%
    \textunderscore\nobreak\hspace{0pt}%
}

FOS\_SOCIAL\_SCIENCE

\renewcommand{\_}{%
    \textunderscore\hspace{0pt}%
}

FOS\_SOCIAL\_SCIENCE

\end{document}