How to use math symbols in a glossary?

Question

I have a document to which I'd like to add a list of variables with short description. Therefore I'd like to use the glossaries package. It works in case the glossary contains only normal text, but since I need sub- and superscripts, I always get the error

Undefined control sequence. }

I just want a glossary with the math variable and a short description next to it in some aligned (tabular like) form.

Any help apprechiated, thanks! Here's a minimal example:

\documentclass{report}
\usepackage{amsmath,amssymb,amsthm,makeidx,amsxtra,amscd}
\usepackage[toc,nonumberlist,nopostdot]{glossaries}
\usepackage{glossary-mcols}
\setglossarystyle{long}

\makeglossaries

\newglossaryentry{firstvar}
{
    name={$\iRab$},
    description={Description 1}
}

\newglossaryentry{secondvar}
{
    name=bw,
    description={Description 2}
}

\newcommand{\iRab}{{}^{}_{I}R^{}_{ab}}

\begin{document}
    \glsaddall
    \printglossary[title=Symbols and Notation]
    \iRab
\end{document}

Relevant .log part :

 (./document.gls [1

\openout3 = `document.ist'.

{/usr/local/texlive/2019/texmf-var/fonts/map/pdftex/updmap/pdftex.map}]
LaTeX Font Info:    Try loading font information for U+msa on input line 5.

(/usr/local/texlive/2019/texmf-dist/tex/latex/amsfonts/umsa.fd
File: umsa.fd 2013/01/14 v3.01 AMS symbols A
)
LaTeX Font Info:    Try loading font information for U+msb on input line 5.

(/usr/local/texlive/2019/texmf-dist/tex/latex/amsfonts/umsb.fd
File: umsb.fd 2013/01/14 v3.01 AMS symbols B
))
! Missing $ inserted.
<inserted text> 
                $
l.26    \iRab

I've inserted a begin-math/end-math symbol since I think
you left one out. Proceed, with fingers crossed.

! Missing $ inserted.
<inserted text> 
                $
l.27 \end{document}

I've inserted a begin-math/end-math symbol since I think
you left one out. Proceed, with fingers crossed.

[2

] (./document.aux) ) 

Answer 1

The problem is not with the glossaries, rather with the new command. You need to fix two things:

1. you need to ensure it's in math mode with \ensuremath
2. You need the new command to appear before the first time it is used.

MWE

\documentclass{report}
\usepackage{amsmath,amssymb,amsthm,makeidx,amsxtra,amscd}
\usepackage[toc,nonumberlist,nopostdot]{glossaries}
\usepackage{glossary-mcols}
\setglossarystyle{long}

\makeglossaries
\newcommand{\iRab}{\ensuremath{{}^{}_{I}R^{}_{ab}}}
\newglossaryentry{firstvar}
{
    name={$\iRab$},
    description={Description 1}
}

\newglossaryentry{secondvar}
{
    name=bw,
    description={Description 2}
}



\begin{document}
    \glsaddall
    \printglossary[title=Symbols and Notation]
    \iRab
\end{document}

Answer 2

With this code you have not any errors with the compilation.

\documentclass{report}
\usepackage{amsmath,amssymb,amsthm,makeidx,amsxtra,amscd}
\usepackage[toc,nonumberlist,nopostdot]{glossaries}
\usepackage{glossary-mcols}
\setglossarystyle{long}
\newcommand{\iRab}{${}^{}_{I}R^{}_{ab}$}
\makeglossaries
\newglossaryentry{firstvar}
{
    name={\ensuremath{\iRab}},
    description={Description 1}
}
\newglossaryentry{secondvar}
{
    name=bw,
    description={Description 2}
}
\begin{document}
    \glsaddall
    \printglossary[title=Symbols and Notation]
    \iRab
\end{document}