A thesaurus (plural thesauri or thesauruses) or synonym dictionary is a reference work for finding synonyms and sometimes antonyms of words.[1] They are often used by writers to help find the best word to express an idea: find the word, or words, by which [an] idea may be most fitly and aptly expressed

Synonym dictionaries have a long history. The word 'thesaurus' was used in 1852 by Peter Mark Roget for his Roget's Thesaurus.

While some thesauri, such as Roget's Thesaurus, group words in a hierarchical taxonomy of concepts, others are organized alphabetically or in some other way.

Most thesauri do not include definitions, but many dictionaries include listings of synonyms.

Some thesauri and dictionary synonym notes characterize the distinctions between similar words, with notes on their "connotations and varying shades of meaning".[3] Some synonym dictionaries are primarily concerned with differentiating synonyms by meaning and usage. Usage manuals such as Fowler’s A Dictionary of Modern English Usage often prescribe appropriate usage of synonyms.

Thesauri are sometimes used to avoid repetition of words, leading to elegant variation, which is often criticized by usage manuals: "writers sometimes use them not just to vary their vocabularies but to dress them up too much".[4]



The word "thesaurus" comes from Latin thēsaurus, which in turn comes from Greek θησαυρός (thēsauros) 'treasure, treasury, storehouse'.[5] The word thēsauros is of uncertain etymology.[5][6]

Until the 19th century, a thesaurus was any dictionary or encyclopedia, as in the Thesaurus Linguae Latinae (Dictionary of the Latin Language, 1532), and the Thesaurus Linguae Graecae (Dictionary of the Greek Language, 1572). It was Roget who introduced the meaning "collection of words arranged according to sense", in 1852.[5]


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 study of synonyms became an important theme in 18th-century philosophy, and Condillac wrote, but never published, a dictionary of synonyms.[7][8]

Some early synonym dictionaries include:

Roget's Thesaurus, first compiled in 1805 by Peter Mark Roget, and published in 1852, follows John Wilkins' semantic arrangement of 1668. Unlike earlier synonym dictionaries, it does not include definitions or aim to help the user to choose among synonyms. It has been continuously in print since 1852, and remains widely used across the English-speaking world.[17] Roget described his thesaurus in the foreword to the first edition:

It is now nearly fifty years since I first projected a system of verbal classification similar to that on which the present work is founded. Conceiving that such a compilation might help to supply my own deficiencies, I had, in the year 1805, completed a classed catalogue of words on a small scale, but on the same principle, and nearly in the same form, as the Thesaurus now published.[18]



Roget's original thesaurus was organized into 1000 conceptual Heads (e.g., 806 Debt) organized into a four-level taxonomy. For example, liability was classed under V.ii.iv: Class five, Volition: the exercise of the will; Division Two: Social volition; Section 4: Possessive Relations; Subsection 4: Monetary relations.[19] Each head includes direct synonyms: Debt, obligation, liability, ...; related concepts: interest, usance, usury; related persons: debtor, debitor, ... defaulter (808); verbs: to be in debt, to owe, ... see Borrow (788); phrases: to run up a bill or score, ...; and adjectives: in debt, indebted, owing, .... Numbers in parentheses are cross-references to other Heads.

The book starts with a Tabular Synopsis of Categories laying out the hierarchy,[20] then the main body of the thesaurus listed by Head, and then an alphabetical index listing the different Heads under which a word may be found: Liable, subject to, 177; debt, 806; duty, 926.[21]

Some recent versions have kept the same organization, though often with more detail under each Head.[22] Others have made modest changes such as eliminating the four-level taxonomy and adding new heads: one has 1075 Heads in fifteen Classes.[23]

Some non-English thesauri have also adopted this model.[24]


Other thesauri and synonym dictionaries are organized alphabetically.

Most repeat the list of synonyms under each word.[25][26][27][28]

Some designate a principal entry for each concept and cross-reference it.[29][30][31]

A third system interfiles words and conceptual headings. Francis March's Thesaurus Dictionary gives for liability: CONTINGENCY, CREDIT–DEBT, DUTY–DERELICTION, LIBERTY–SUBJECTION, MONEY, each of which is a conceptual heading.[32] The CREDIT—DEBT article has multiple subheadings, including Nouns of Agent, Verbs, Verbal Expressions, etc. Under each are listed synonyms with brief definitions, e.g. "Credit. Transference of property on promise of future payment." The conceptual headings are not organized into a taxonomy.

Benjamin Lafaye's Synonymes français (1841) is organized around morphologically related families of synonyms (e.g. logis, logement),[33] and his Dictionnaire des synonymes de la langue française (1858) is mostly alphabetical, but also includes a section on morphologically related synonyms, which is organized by prefix, suffix, or construction.[8]

Contrasting senses

Before Roget, most thesauri and dictionary synonym notes included discussions of the differences among near-synonyms, as do some modern ones.[28][27][26][3]

A few modern synonym dictionaries, notably in French, are primarily devoted to discussing the precise demarcations among synonyms.[34][8]

Additional elements

Some include short definitions.[32]

Some give illustrative phrases.[28]

Some include lists of objects by category, e.g. breeds of dogs.[28]

The Historical Thesaurus of English (2009) is organized taxonomically, and includes the date when each word came to have a given meaning. It has the novel and unique goal of "charting the semantic development of the huge and varied vocabulary of English".[35]


Bilingual synonym dictionaries are designed for language learners. One such dictionary gives various French words listed alphabetically, with an English translation and an example of use.[36] Another one is organized taxonomically with examples, translations, and some usage notes.[37]

Information science and natural language processing

In library and information science, a thesaurus is a kind of controlled vocabulary.

A thesaurus can form part of an ontology and be represented in the Simple Knowledge Organization System (SKOS).[38]

Thesauri are used in natural language processing for word-sense disambiguation[39] and text simplification for machine translation systems.[40]

See also



  1. ^ Reid, Kyra. "Synonym Dictionary Words and Phrases" . Power Thesaurus. Retrieved 18 September 2012.
  2. ^ Roget, Peter. 1852. Thesaurus of English Language Words and Phrases.
  3. ^ a b American Heritage Dictionary of the English Language, 5th edition, Houghton Mifflin Harcourt 2011, ISBN 9780547041018, p. xxvii
  4. ^ Edwin L. Battistella, "Beware the thesaurus", OUPblog, "Oxford University Press's Academic Insights for the Thinking World", February 11, 2018
  5. ^ a b c "thesaurus" . Online Etymology Dictionary.
  6. ^ R. S. P. Beekes, Etymological Dictionary of Greek, Brill, 2009, p. 548.
  7. ^ Embleton
  8. ^ a b c B. Lafaye, Dictionnaire des synonymes de la langue française, Hachette 1869, 3rd edition
  9. ^ John Wilkins, An Essay Towards a Real Character, and a Philosophical Language, London 1668 full text
  10. ^ John Wilkins, William Lloyd (anonymously), An Alphabetical Dictionary Wherein all English Words According to their Various Significations, Are either referred to their Places in the Philosophical Tables, Or explained by such Words as are in those Tables, London 1668 full text
  11. ^ Natascia Leonardi, "An Analysis of a Seventeenth Century Conceptual Dictionary with an Alphabetical List of Entries and a Network Definition Structure: John Wilkins' and William Lloyd's An Alphabetical Dictionary (1668)" in Historical Dictionaries and Historical Dictionary Research, papers from the International Conference on Historical Lexicography and Lexicology, University of Leicester, 2002, Max Niemeyer Verlag 2004, ISBN 3484391235, p. 39-52
  12. ^ Gabriel Girard, La Justesse de la langue françoise, ou les différentes significations des mots qui passent pour synonymes, Paris 1718, full text
  13. ^ John Trusler (anonymously), The Difference between Words esteemed Synonyms, in the English Language; and the proper choice of them determined, London, 1766 full text
  14. ^ Hester Lynch Piozzi, British Synonymy; or, an Attempt Regulating the Choice of Words in Familiar Conversation, Dublin 1794 full text
  15. ^ James Leslie, Dictionary of the Synonymous Words and Technical Terms in the English Language, Edinburgh, 1806 full text
  16. ^ George Crabb, English Synonyms Explained, in Alphabetical Order with Copious Illustrations and Examples Drawn from the Best Writers, 2nd edition, London 1818 full text
  17. ^ "Introduction - Oxford Scholarship" . doi:10.1093/acprof:oso/9780199254729.001.0001/acprof-9780199254729-chapter-1 . Retrieved 26 March 2018.
  18. ^ Lloyd 1982, p. xix[full citation needed]
  19. ^ Peter Mark Roget, Thesaurus of English words and phrases, classified so as to facilitate the expression of ideas, 1853, V.ii.iv, p. 204
  20. ^ Roget, op.cit. p. xxvi
  21. ^ Roget, op.cit. p. 349
  22. ^ e.g., George Davidson, ed., Thesaurus of English words and phrases (150th Anniversary Edition), Penguin, 2002, ISBN 0141004428, p. 454
  23. ^ Barbara Ann Kipfer, ed., Roget's International Thesaurus, 7th edition, Collins Reference, 2010, ISBN 9780061715228
  24. ^ Daniel Péchoin, Thésaurus Larousse, Larousse 1991, ISBN 9782033201074
  25. ^ Longman Synonym Dictionary, Rodale Press and Longman Group, 1986, ISBN 0582893224
  26. ^ a b Charlton Laird, Michael Agnes, eds., Webster's New World Roget's A-Z Thesaurus, Macmillan USA, 3rd edition, 1971, ISBN 0028632818
  27. ^ a b Christine A. Lindberg, The Oxford American Thesaurus of Current English, Oxford University Press, 1999, ISBN 0195133757
  28. ^ a b c d Oxford Thesaurus of English, 3rd edition, 2009, ISBN 9780199560813
  29. ^ Merriam-Webster's Dictionary of Synonyms : Choose Words with Precision, 1994, ISBN 0877799067 uses an asterisk
  30. ^ Henri Bertaud du Chazaud, Dictionnaire de synonyms et contraires, Le Robert "Les Usuels", 1998, ISBN 2850364568
  31. ^ Roger Boussinot, Dictionnaire des synonymes, analogies et antonymes, Bordas 1981, ISBN 2040120092
  32. ^ a b Francis Andrew March, Francis A. March, Jr., March's Thesaurus and Dictionary of the English Language (issued under the editorial supervision of Norman Cousins), Doubleday, 1968, p. 598 full text, 1906 edition
  33. ^ Pierre Benjamin Lafaye, Synonymes français, Paris 1841 full text
  34. ^ Henri Bénac, Dictionnaire des synonymes, Hachette 1956, ISBN 2010112199 (1982 edition)
  35. ^ Christian Kay, Jane Roberts, Michael Samuels, Irené Wotherspoon, Historical Thesaurus of the Oxford English Dictionary, Oxford University Press 2009, ISBN 9780199208999, p. ix
  36. ^ R.E. Batchelor, M.H. Offord, Using French Synonyms, Cambridge University Press, 1993, ISBN 0521372771
  37. ^ Marie-Noëlle Lamy, The Cambridge French-English Thesaurus, Cambridge University Press, 1998, ISBN 0521563488
  38. ^ Miles, Alistair; Bechhofer, Sean (2009). "SKOS simple knowledge organization system reference" . W3C recommendation. 18: W3C.
  39. ^ Yarowsky, David. "Word-sense disambiguation using statistical models of Roget's categories trained on large corpora ." Proceedings of the 14th conference on Computational linguistics-Volume 2. Association for Computational Linguistics, 1992.
  40. ^ Siddharthan, Advaith. "An architecture for a text simplification system." Language Engineering Conference, 2002. Proceedings. IEEE, 2002.

External links

Categories: Thesauri | Reference works | Dictionaries by type | Lexical semantics

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