# thesaurus

/θəˈsɔɹəs/ (US) · /θɛsˈɔːɹəs/ (UK)

Source: https://englishreference.com/word/thesaurus
Updated: 2026-08-27

## Senses

### 1. book of synonyms

noun · CEFR B2

a book or website that lists words with the same or similar meanings.

For teachers: a reference work containing lists of words with similar meanings, often used to avoid repetition or to find a more precise term.

- I used a thesaurus to find a better word than 'big' for my essay.
- The student consulted a thesaurus to diversify her vocabulary, replacing repetitive adjectives with more nuanced alternatives throughout the manuscript.

Usage: The plural can be either 'thesauruses' or 'thesauri'.

### 2. data classification

noun · CEFR C1 · Technical

a list of specific terms used to organize and search for information in a database.

For teachers: a controlled vocabulary of terms used in information science to facilitate the indexing and retrieval of documents within a specific domain.

- The library uses a special thesaurus to categorize all their science books.
- The database architect developed a hierarchical thesaurus to ensure that all technical documents were indexed under standardized subject headings.

Teaching tip: This sense is specific to library science and information technology; general learners will rarely encounter it outside of professional contexts.

## Examples

- I looked up the word 'happy' in the thesaurus.
- The writer used a digital thesaurus to find a more precise word for 'big' in her novel.
- While a standard dictionary provides definitions, a thesaurus serves as a linguistic compass, guiding the author toward the most appropriate synonym for the specific tone they wish to achieve.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.