star''');
 to_tsquery
------------
 'sn'
</screen>

    Notice that <literal>supernova star</literal> matches <literal>supernovae
    stars</literal> in <literal>thesaurus_astro</literal> because we specified
    the <literal>english_stem</literal> stemmer in the thesaurus definition.
    The stemmer removed the <literal>e</literal> and <literal>s</literal>.
   </para>

   <para>
    To index the original phrase as well as the substitute, just include it
    in the right-hand part of the definition:

<screen>
supernovae stars : sn supernovae stars

SELECT plainto_tsquery('supernova star');
       plainto_tsquery
-----------------------------
 'sn' &amp; 'supernova' &amp; 'star'
</screen>
   </para>

  </sect3>

  </sect2>

  <sect2 id="textsearch-ispell-dictionary">
   <title><application>Ispell</application> Dictionary</title>

   <para>
    The <application>Ispell</application> dictionary template supports
    <firstterm>morphological dictionaries</firstterm>, which can normalize many
    different linguistic forms of a word into the same lexeme.  For example,
    an English <application>Ispell</application> dictionary can match all declensions and
    conjugations of the search term <literal>bank</literal>, e.g.,
    <literal>banking</literal>, <literal>banked</literal>, <literal>banks</literal>,
    <literal>banks'</literal>, and <literal>bank's</literal>.
   </para>

   <para>
    The standard <productname>PostgreSQL</productname> distribution does
    not include any <application>Ispell</application> configuration files.
    Dictionaries for a large number of languages are available from <ulink
    url="https://www.cs.hmc.edu/~geoff/ispell.html">Ispell</ulink>.
    Also, some more modern dictionary file formats are supported &mdash; <ulink
    url="https://en.wikipedia.org/wiki/MySpell">MySpell</ulink> (OO &lt; 2.0.1)
    and <ulink url="https://hunspell.github.io/">Hunspell</ulink>
    (OO &gt;= 2.0.2).  A large list of dictionaries is available on the <ulink
    url="https://wiki.openoffice.org/wiki/Dictionaries">OpenOffice
    Wiki</ulink>.
   </para>

   <para>
    To create an <application>Ispell</application> dictionary perform these steps:
   </para>
   <itemizedlist spacing="compact" mark="bullet">
    <listitem>
     <para>
      download dictionary configuration files. <productname>OpenOffice</productname>
      extension files have the <filename>.oxt</filename> extension. It is necessary
      to extract <filename>.aff</filename> and <filename>.dic</filename> files, change
      extensions to <filename>.affix</filename> and <filename>.dict</filename>. For some
      dictionary files it is also needed to convert characters to the UTF-8
      encoding with commands (for example, for a Norwegian language dictionary):
<programlisting>
iconv -f ISO_8859-1 -t UTF-8 -o nn_no.affix nn_NO.aff
iconv -f ISO_8859-1 -t UTF-8 -o nn_no.dict nn_NO.dic
</programlisting>
     </para>
    </listitem>
    <listitem>
     <para>
      copy files to the <filename>$SHAREDIR/tsearch_data</filename> directory
     </para>
    </listitem>
    <listitem>
     <para>
      load files into PostgreSQL with the following command:
<programlisting>
CREATE TEXT SEARCH DICTIONARY english_hunspell (
    TEMPLATE = ispell,
    DictFile = en_us,
    AffFile = en_us,
    Stopwords = english);
</programlisting>
     </para>
    </listitem>
   </itemizedlist>

   <para>
    Here, <literal>DictFile</literal>, <literal>AffFile</literal>, and <literal>StopWords</literal>
    specify the base names of the dictionary, affixes, and stop-words files.
    The stop-words file has the same format explained above for the
    <literal>simple</literal> dictionary type.  The format of the other files is
    not specified here but is available from the above-mentioned web sites.
   </para>

   <para>
    Ispell dictionaries usually recognize a limited set of words, so they
    should be followed by another broader dictionary; for
    example, a Snowball dictionary,