A thesaurus can be: 1. A work of reference presented as a treasure house of information about words 2. A work of reference containing lists of associated, usually undefined, words (such as synonyms) arranged thematically 3. A work of reference containing such lists but presented alphabetically 4. In information technology, an alphabetic index list of key terms, through which information of a specialist nature can be retrieved from a database. In such a thesaurus, terms are commonly linked associatively by cross-reference through such relations as synonymy and antonymy 5. In word processing, a stored list of synonyms and antonyms, to be consulted in the preparation of texts and provided as a service comparable to a spelling checker (McArthur 1992, p. 1040 f.)