Full-text Search - Thesaurus relationships

Hi,

The documentation[1] says thesaurus can include informations of terms
relationships such broader terms, preferred terms ...

I haven't been able to find out how to exploit those relationship in
postgres. Is there any keyword to and associated syntax to make use of
them ?

Thanks,

[1]: https://www.postgresql.org/docs/current/static/textsearch-dictionaries.html#TEXTSEARCH-THESAURUS
--
nicolas