TeX and LaTeX math delimiters

.. _tex-delimiters:

############################# TeX and LaTeX math delimiters #############################

By default, the TeX processor uses the LaTeX math delimiters, which are \(...\) for in-line math, and \[...\] for displayed equations. It also recognizes the TeX delimiters $$...$$ for displayed equations, but it does not define $...$ as in-line math delimiters. That is because dollar signs appear too often in non-mathematical settings, which could cause some text to be treated as mathematics unexpectedly. For example, with single-dollar delimiters, "... the cost is $2.50 for the first one, and $2.00 for each additional one ..." would cause the phrase "2.50 for the first one, and" to be treated as mathematics since it falls between dollar signs. For this reason, if you want to use single dollar signs for in-line math mode, you must enable that explicitly in your configuration:

.. code-block:: javascript

window.MathJax = {
  tex: {
    inlineMath: {'[+]': [['$', '$']]}
  }
};

This adds the single dollar signs as additional in-line math delimiters.

You can use \$ to prevent a dollar sign from being treated as a math delimiter within the text of your web page; e.g., use "... the cost is \$2.50 for the first one, and \$2.00 for each additional one ..." to prevent these dollar signs from being used as math delimiters in a web page where dollar signs have been configured to be in-line delimiters.

Alternatively, putting the dollar sign inside a <span> tag would also prevent it from being treated as a math delimiter. That is,

.. code-block:: html

... the cost is <span>$</span>2.50 for the first one, and <span>$</span>2.00 for each additional one ...

would also prevent the dollar signs from being treated as math delimiters. This is because MathJax only matches delimiters that appear within the same parent element of the HTML page, so isolating the dollar sign inside a tag prevents it from matching with another dollar sign to delimit a mathematical expression.

In version 3 and below, TeX expressions can not contain HTML elements (other than , <wbr>, and comments), but in version 4, a new texhtml extension provides a means of including HTML notation within TeX expressions. See the :ref:tex-texhtml page for details. Placing a dollar sign with a <span> would still prevent it from being treated as a delimiter, even with the texhtml extension.

Note that, as opposed to true LaTeX, MathJax processes all environments when wrapped inside math delimiters, even those like \begin{equation}...\end{equation} that are supposed to be used to initiate math mode. By default, MathJax will also render all environments outside of delimiters, e.g., \begin{matrix}...\end{matrix} would be processed even if it is not in math mode delimiters, though you are encouraged to use proper delimiters for these cases to make your files more compatible with actual LaTeX. This functionality can be controlled via the processEnvironments option in the :ref:tex configuration options <tex-options>.

See the :ref:tex configuration options <tex-options> page for additional configuration parameters that you can specify for the TeX input processor.

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