Linking taxonomy terms that appear in content
You mean automatically? You probably want something like the glossary module


  The glossary module scans posts for glossary terms (including
  synonyms). The glossary indicator is inserted after every found term,
  or the term itself is turned into an indicator depending on the site
  settings. ... The glossary uses Drupal's built in taxonomy feature, so
  you can organize your terms in a Drupal vocabulary.