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This article is about thesauri for general or literary applications; for thesauri designed for information retrieval, see Thesaurus (information retrieval)
In general usage, a thesaurus (plural "thesauri") is a reference work that lists words grouped together according to similarity of meaning (containing synonyms and sometimes antonyms), in contrast to a dictionary, which provides definitions for words, and generally lists them in alphabetical order.The main purpose of such reference works is to help the user “to find the word, or words, by which [an] idea may be most fitly and aptly expressed” – to quote Peter Roget, architect of the best known thesaurus in the English language.
In antiquity, Philo of Byblos authored the first text that could now be called a thesaurus. In Sanskrit, the Amarakosha is a thesaurus in verse form, written in the 4th century. The first example of the modern genre, Roget's Thesaurus, was compiled in 1805 by Peter Mark Roget, and published in 1852. Entries in Roget's Thesaurus are listed conceptually rather than alphabetically.
Although including synonyms, a thesaurus should not be taken as a complete list of all the synonyms for a particular word. The entries are also designed for drawing distinctions between similar words and assisting in choosing exactly the right word. Unlike a dictionary, a thesaurus entry does not give the definition of words.
The word "thesaurus" is derived from 16th-century New Latin, in turn from Latin thēsaurus, which is the latinisation of the Greek θησαυρός (thēsauros), literally "treasure store", generally meaning a collection of things which are of big importance or value (and thus the medieval rank of thesaurer was a synonym for treasurer). This meaning has been largely supplanted by Roget's usage of the term.
List of thesauri 
- Thesaurus of English Words & Phrases (ed. P. Roget); ISBN 0-06-272037-6, see: Roget's Thesaurus.
- World Thesaurus (ed. C. Laird); ISBN 0-671-51983-2. This edition has been used in successive editions since 1971 by Webster's:
- Oxford American Desk Thesaurus (ed. C. Lindberg); ISBN 0-19-512674-2
- Oxford Paperback Thesaurus: Third Edition; ISBN 978-0-19-861425-8
- Random House Word Menu by Stephen Glazier; ISBN 0-679-40030-3
- Historical Thesaurus of English (HTE)
- The Well-Spoken Thesaurus by Tom Heehler; ISBN 978-1-4022-4305-9
See also 
- Controlled vocabulary
- Knowledge Organization Systems
- Ontology (computer science)
- Simple Knowledge Organisation System
- Thesaurus (information retrieval)
- ISO 25964
- Roget, Peter. 1852. Thesaurus of English Language Words and Phrases
|Look up thesaurus in Wiktionary, the free dictionary.|
- Aiksaurus: open source and online thesaurus
- Asadz Online Thesaurus
- Collins Unabridged English Thesaurus
- How to say big online synonym finder
- Macmillan Dictionary thesaurus
- Online thesaurus based on the OpenOffice.org spell checker Hunspell
- Powerthesaurus voting-based thesaurus with extra semantic relations and word definitions
- Snappy Words Free English Dictionary and Thesaurus
- Sinonimi open source online thesaurus
- Synonym Finder
- TemaTres: open source thesaurus management
- Thesaurus Builder full multilingual thesaurus management software
- Thesaurus.com The largest online English thesaurus
- Word Associations Network
- Yahoo! Education Thesaurus