What does thesaurus mean?
A thesaurus is a reference book or digital resource that organizes vocabulary according to meaning, usually placing synonyms, antonyms, and closely related expressions together. Writers and students commonly use one to improve precision, avoid repetition, or find the strongest term for an idea. Although dictionaries primarily define words and explain their usage, thesauri emphasize relationships among words and may also include quotations, examples, and distinctions between confusable terms. The word also has a broader figurative sense: a collection so extensive or well organized that it functions as a storehouse of language. Historically, a thesaurus meant a treasury or storehouse of valuable possessions. That older image still explains its modern appeal: it gathers many useful alternatives in one place. The term is now firmly established in both everyday writing and publishing, while electronic thesauri have expanded access beyond specialist reference shelves.
nounA reference book or digital resource that organizes words according to meaning, usually grouping synonyms, antonyms, and closely related expressions. It may also include definitions, examples, quotations, and guidance on usage.
- A reference book or digital resource that lists words by meaning and provides synonyms, antonyms, and related expressions.
- A large or systematically organized collection of words, especially on a particular subject.
- Archaically, a treasury or storehouse of valuable possessions.
"A careful editor reached for the thesaurus only when ordinary synonyms felt imprecise."
"She checked the thesaurus before choosing a more precise term."
"The archive's oral-history collection became a thesaurus of everyday speech."
The traditional plural is “thesauri,” while “thesauruses” is also accepted.
"The library has several thesauri covering specialized vocabulary."
Born from a Greek word for treasure, a thesaurus is now a treasure trove of ways to say the same thing—and often much more.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does thesaurus come from?
The English word comes from Latin thesaurus, meaning “treasure” or “treasury,” which was borrowed from Greek thesauros, meaning “treasure” or “storehouse.” In English, the word initially referred to a treasury or storehouse of wealth and later came to denote a collection or systematized store of words. Treasury, thesauric, and related forms reflect the same ancient source.
How thesaurus is actually used
The term is neutral in register and may refer to printed or electronic resources. Figurative use suggests a large, organized abundance. Traditional thesauri emphasize synonyms and antonyms, while many modern digital ones also contain broader dictionary-style information.
Easily confused with thesaurus
A treasury is a place or institution holding funds, whereas a thesaurus is primarily a collection or systematic arrangement of words.