 label that is not
numeric or begins with ``#``.


Substitutions
-------------

reST supports "substitutions" (:duref:`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&