thesaurus

noun

Etymology: 16th century, borrowed from Latin thēsaurus, from Ancient Greek θησαυρός (thēsaurós, “storehouse, treasure”); its current English usage/meaning was established soon after the publication of Peter Roget's Thesaurus of English Words and Phrases in 1852. Doublet of treasure.

1. A publication that provides synonyms (and sometimes antonyms and other semantic relations) for the words of a given language.

   “"Roget" is the leading brand name for a print English thesaurus that lists words under general concepts rather than just close synonyms.”

   “As reference books go, the thesaurus has had a somewhat checkered history, in fact, and has probably occasioned as much bad writing as good.”

2. A dictionary or encyclopedia.
3. A hierarchy of subject headings: canonical titles of themes and topics, the titles serving as search keys.