निरंजन
```
\documentclass{article}
\renewcommand{\&}{\textbf{\&}}
\begin{document}
\&
\end{document}
```
Pretty basic question. I have looked for [this](https://tex.stackexchange.com/questions/24247/tex-capacity-exceeded-sorry-input-stack-size-5000) on TeX.SE, but it doesn't capture my problem well. Please explain why I am getting this error. Also how to change all the `\&`s to bold ones in the preamble itself?
Top Answer
samcarter
The problem is that inside your command definition you use the redefined command - this creates an infinite loop.
A simple solution is to store the old definition of the command like this:
```
\documentclass{article}
\let\oldampersand\&
\renewcommand{\&}{\textbf{\oldampersand}}
\begin{document}
ge \& erj
\end{document}
```