the·​sau·​rus thi-ˈsȯr-əs How to pronounce thesaurus (audio)
plural thesauri thi-ˈsȯr-ˌī How to pronounce thesaurus (audio)
or thesauruses thi-ˈsȯr-ə-səz How to pronounce thesaurus (audio)
: a book of words or of information about a particular field or set of concepts
especially : a book of words and their synonyms
: a list of subject headings or descriptors usually with a cross-reference system for use in the organization of a collection of documents for reference and retrieval
thesaural adjective

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In the early 19th century, archaeologists borrowed the Latin word thesaurus to denote an ancient treasury, such as that in a temple. Soon after, the word was metaphorically applied to a book containing a treasury of words or information about a particular field. In 1852, the English scholar Peter Mark Roget published his Thesaurus of English Words and Phrases, in which he listed a treasury of semantically related words organized into numerous categories. This work led to the common acceptance of the term thesaurus to refer to "a book of words and their synonyms." The word developed another meaning in the 1950s, when thesaurus began being used in the field of word processing to refer to a list of related terms used for indexing and retrieval.

Examples of thesaurus in a Sentence

Recent Examples on the Web There might be a great many creative epithets used to denigrate Asian people, as I was reminded about recently when watching the 2008 film Gran Torino, in which Clint Eastwood plays a cantankerous old man who owns a thesaurus full of them—but the directness of chink feels among the worst. Jeremy Gordon, The Atlantic, 26 Feb. 2024 At their simplest, these programs mask plagiarism through liberal use of a thesaurus; replace enough words with synonyms and hopefully nobody will ever find the original source. Charles Seife, Scientific American, 28 Sep. 2023 But the band’s coolness has been constantly called into question by male rock critics high on their own thesaurus finds, and lazy SNL skits about lesbian culture. Faran Krentcil, Harper's BAZAAR, 27 July 2023 Other popular titles include thesauruses, small business startup, drawing, exercise, fiction of all kinds and religion, according to the website. Mike Jones, Arkansas Online, 19 June 2023 See all Example Sentences for thesaurus 

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'thesaurus.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


New Latin, from Latin, treasure, collection, from Greek thēsauros

First Known Use

circa 1823, in the meaning defined at sense 2

Time Traveler
The first known use of thesaurus was circa 1823


Dictionary Entries Near thesaurus

Cite this Entry

“Thesaurus.” Dictionary, Merriam-Webster, Accessed 23 Jun. 2024.

Kids Definition


the·​sau·​rus thi-ˈsȯr-əs How to pronounce thesaurus (audio)
plural thesauri -ˈsȯ(ə)r-ˌī How to pronounce thesaurus (audio)
or thesauruses -ˈsȯr-ə-səz How to pronounce thesaurus (audio)
: a book of words and their synonyms

from scientific Latin thesaurus "treasury, storehouse, book of words," from Latin thesaurus "treasure, collection," from Greek thēsauros (same meaning) — related to treasure

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