Thesaurus

A thesaurus (aka a synonym dictionary) is a publication (printed or online) that provides lists of synonyms (and sometimes antonyms or other semantically-related words) for given words in a particular language.

Quotes

Rarely used words, non-English words, names, obsolete and unidiomatic expressions, phrases: all are thrown in together along with common words without any apparent principle of selection. For example, in the fourth edition of Roget's International Thesaurus – one of the best of the conceptually arranged works – we find included under the subheading orator: Demosthenes, Cicero, Franklin D. Roosevelt, Winston Churchill, William Jennings Bryan. Why not Pericles and Billy Graham? When one starts to include types of things, where does one stop? There is actually a list of insects (paragraph 414.36), which is even more of a random sampling than that of orators. Such works are a potpourri of everything the compiler can think of.
- Sidney Landau, Dictionaries: the Art and Craft of Lexicography. Cambridge University Press. 1989. p. 108.

In the search for words, thesauruses are useful things, but they don't talk about the words they list. They are also dangerous. They can lead you to choose a polysyllabic and fuzzy word when a simple and clear one is better. The value of a thesaurus is not to make a writer seem to have a vast vocabulary of recondite words. The value of a thesaurus is in the assistance it can give you in finding the best possible word for the mission that the word is supposed to fulfill. Writing teachers and journalism courses have been known to compare them to crutches and to imply that no writer of any character or competence would use them. At best, thesauruses are mere rest stops in the search for the mot juste. Your destination is the dictionary.
- John McPhee, (2013)"Draft no. 4". The New Yorker 29: 32–38. (quote from p. 34)

Thesauri are valuable structures for Information Retrieval systems. A thesaurus provides a precise and controlled vocabulary which serves to coordinate document indexing and document retrieval. In both indexing and retrieval, a thesaurus may be used to select the most appropriate terms. Additionally, the thesaurus can assist the searcher in reformulating search strategies if required. This chapter first examines the important features of thesauri. This should allow the reader to differentiate between thesauri. Next, a brief overview of the manual thesaurus construction process is given. Two major approaches for automatic thesaurus construction have been selected for detailed examination. The first is on thesaurus construction from collections of documents, and the second, on thesaurus construction by merging existing thesauri. These two methods were selected since they rely on statistical techniques alone and are also significantly different from each other.
- Padmini Srinivasan, "Chapter 9. Thesaurus construction". Information Retrieval: data structures and algorithms. Prentice Hall. 1992. pp. 161-218. edited by William B. Frakes and Ricardo Baeza-Yates ISBN 0134638379 book description, amazon.com