Adding "\exists !" to the nomenclature

Question

I get several errors on trying to add "\exists !" to the nomenclature.

Does someone can help?

Here my MWE (sorry for the makeindex, I don't want to change my build-command and without changing it, it completely fails)

\documentclass{article}
\usepackage{makeidx}
\usepackage{nomencl}

\makeindex

\makenomenclature

\begin{document}
dummy
\nomenclature{$\exists$}{exists}
%\nomenclature{$\exists !$}{exists exactly one} %error
%\nomenclature{$\exists!$}{exists exactly one} %error
\nomenclature{$\exists$!}{exists exactly one} %no effect

\printnomenclature
\end{document}

---

Solution:

\nomenclature{$\exists"!$}{exists exactly one}

Answer 1

Some characters are special for MakeIndex:

! @ | ( ) "

and they should be quoted when in an index entry; it doesn't matter whether it is \nomenclature, because it uses the same framework as \index. Quoting is obtained by prefixing the special character with ". Thus

\nomenclature{$\exists"!$}{exists exactly one}

should do.