thesaurus

A thesaurus is a reference work or database that organizes words by their semantic relationships. Its primary purpose is to help writers find synonyms and related words, expand their vocabulary, and vary diction while maintaining nuance and tone.

There are monolingual thesauri (in a single language) and bilingual or multilingual ones. They can be general-purpose or domain-specific (technical, literary, medical). They appear as printed volumes, online resources, and integrated tools in word processors and browsers.

Most thesauri present entries with a headword and a list of senses, followed by synonyms, related terms, and sometimes antonyms. The organization is often by sense rather than simply alphabetically; several entries distinguish precise synonyms from near relatives and note connotation, formality, and usage.

The best-known early thesaurus is Roget's Thesaurus, first published in 1852 by Peter Mark Roget. Roget grouped words by conceptual ideas and classes rather than by alphabetical order of synonyms. The work influenced many later dictionaries and thesauri and spurred development toward digitally searchable resources.

In practice, a thesaurus is a tool for writing and editing, helping to avoid repetition and find a word that matches intended meaning, tone, and register. However, it does not replace careful consideration of precise definitions and usage, and users should verify differences in sense, nuance, and collocation.