# Display math should end with $$

## Contents

# Introduction

TeX engines have two ways of typesetting mathematics:

*inline math mode*where the mathematical content is contained within a paragraph, and*display math mode*where mathematical material is displayed separately, with additional space above or below it.

*Traditionally*, in the early days of TeX, mathematics intended to be typeset *inline*, typically within a paragraph, was surrounded by single `$`

characters: `$ inline math content...$`

and mathematics destined for *display* was surrounded by double `$`

characters: `$$ display math content...$$`

.

# Cause of the error `Display math should end with $$`

The error message `Display math should end with $$`

is generated by TeX engines when they try to finish typesetting some display math material but are unable to cleanly exit from display math mode due to incorrect TeX markup: as the error message indicates, the material to be typeset as display math has not been terminated with a second `$$`

pair.

## Examples: single error

This error is demonstrated in the following examples:

```
\documentclass{article}
\usepackage[textwidth=8cm]{geometry}
\begin{document}
\noindent \verb|$$ E=mc^2$| generates an error because the math is
started by \texttt{\$\$} but terminated by a single \texttt{\$}:
$$ E=mc^2$
\noindent\verb|$$ E=mc^2$ $| also generates an error because of the space between
the terminating \texttt{\$} characters:
$$ E=mc^2$ $
\end{document}
```

Open this **error-generating** example in Overleaf

This example produces the following output (image edited to highlight both errors):

## Example: two errors

**Note**: In some circumstances you may *also* see the related error Missing $ inserted, as the following example demonstrates by writing `$$E=mc^2`

, which omits both terminating `$`

characters:

```
\documentclass{article}
\usepackage[textwidth=8cm]{geometry}
\begin{document}
\noindent The following example omits both terminating \texttt{\$} characters, triggering the errors \texttt{Missing \$ inserted} and \texttt{Display math should end with \$\$.}
$$E=mc^2
\end{document}
```

Open this **error-generating** example in Overleaf

This example produces the following output:

# Solution

For the errors demonstrated above, the fix is straightforward—make sure you add the closing `$$`

at the end of your display math:

```
\documentclass{article}
\begin{document}
\noindent The solution is to ensure correct termination of the
display math by writing \verb|$$E=mc^2$$|:
$$E=mc^2$$
\end{document}
```

Open this **corrected** example in Overleaf

# Avoid using `$`

characters to typeset mathematics

Nowadays, standard (accepted) best practice is to *avoid* using explicit `$`

characters to typeset mathematics and use LaTeX *delimiters* instead, particularly for display math:

- for
**display math**: write`\[ display math content \]`

instead of`$$`

*display*math content...$$ - for
**inline math**: write`\( inline math content \)`

instead of`$`

*inline*math content...$

In reality, the LaTeX delimiters `\(`

, `\)`

, `\[`

and `\]`

are single-character *macros* which provide a sort of “insulating wrapper” around single and double `$`

characters. The LaTeX definitions of those delimiters (macros) do actually contain `$`

characters but with additional code that runs some tests/checks. They also generate LaTeX’s error message `Bad math environment delimiter`

. Using these delimiters (macros) has additional advantages because they can be redefined, perhaps temporarily, to achieve special effects.

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