I would like to label an equation with an arbitrary symbol, rather than a number, or letter. Is this possible?

# [Tex/LaTex] Label equation with a symbol

cross-referencingequationssymbols

#### Related Solutions

I would recommend using the `\tag`

macro to directly insert the equation number.

```
\documentclass{article}
\usepackage{amsmath,amssymb}
\numberwithin{equation}{section}
\begin{document}
\section{Section A}
\begin{align}
z^2&= x^2 + y^2 \\
z^2 &= x^2 + y^2 \tag{\theequation'}
\end{align}
\end{document}
```

As per @barbarabeeton 's answer, the `'`

should be `\prime`

as:

```
\documentclass{article}
\usepackage{amsmath,amssymb}
\numberwithin{equation}{section}
\begin{document}
\section{Section A}
\begin{align}
z^2&= x^2 + y^2 \\
z^2 &= x^2 + y^2 \tag{\theequation${}^\prime$}
\end{align}
\begin{equation}
z^2= x^2 + y^2
\end{equation}
\end{document}
```

Incidentally, the `\theequation`

is the way to access directly the formatted `equation`

counter. This works with any counter you're using, `\the<counter_name>`

will call the formatted counter. This is the reason `\theequation`

resulted in `1.1`

and not just `1`

, which is the value of the counter `equation`

.

You *can* do it (but only for equations in any of the `amsmath`

environments). But it is wrong, very wrong: you should think ahead before tweaking this way the cross reference mechanism. When you search for labels, you'll have no clue what each one refers to without first knowing what section the reference/label appears in.

```
\documentclass{article}
\usepackage{amsmath}
\usepackage{etoolbox}
\newcounter{dummysec}
\preto\section{\stepcounter{dummysec}}
\makeatletter
\def\label@in@display#1{%
\ifx\df@label\@empty\else
\@amsmath@err{Multiple \string\label's:
label '\df@label' will be lost}\@eha
\fi
\xdef\df@label{\thedummysec-\unexpanded{#1}}%
}
\renewcommand{\eqref}[1]{\textup{\tagform@{\ref{\thedummysec-#1}}}}
\makeatother
\begin{document}
\section*{first section}
Here is an equation
\begin{equation}\label{a1}
E=mc^2
\end{equation}
where \eqref{a1} obtained by ....
\section*{second section}
Here is another equation
\begin{equation}\label{a1}
a^2=b^2+c^2
\end{equation}
in \eqref{a1} we have ....
\end{document}
```

## Best Answer

Perhaps something like this.