`ref &lt;substitution-definitions&gt;`), which
are pieces of text and/or markup referred to in the text by ``|name|``.  They
are defined like footnotes with explicit markup blocks, like this::

   .. |name| replace:: replacement *text*

or this::

   .. |caution| image:: warning.png
                :alt: Warning!

See the :duref:`reST reference for substitutions &lt;substitution-definitions&gt;`
for details.

If you want to use some substitutions for all documents, put them into
:confval:`rst_prolog` or put