Subject headings tend to be broader in scope describing whole books, while thesauri tend to be more specialized covering very specific disciplines.
en.wikipedia.org They are used in subject indexing schemes, subject headings, thesauri, taxonomies and other forms of knowledge organization systems.
en.wikipedia.org Controlled vocabularies (dictionaries and thesauri), and ontologies allow broader terms, narrower terms, and related terms to be incorporated into queries.
en.wikipedia.org There are other types of dictionaries that don't fit neatly in the above distinction, for instance bilingual (translation) dictionaries, dictionaries of synonyms (thesauri), or rhyming dictionaries.
en.wikipedia.org For each concept, the thesauri provided the usual lexical and semantic information: preferred labels, synonyms and notes, broader and related concepts, etc.
en.wikipedia.org