A synonym finder, or thesaurus, is a type of dictionary or reference book that enables the reader to find words of the same or similar meaning. It provides alternative words that allow a writer to avoid using the same word repeatedly. Synonyms may be a single word or a phrase.
Perhaps the best-known such work is Roget's Thesaurus, the creation of an English doctor named Peter Mark Roget. The first edition was published in 1852, and the book is still published today. Many synonym finders, like Roget's Thesaurus, provide a list of antonyms, which are words with the opposite meaning of the word chosen.