Adding search terms to a user' s search. Query expansion is the process of a search engine adding search terms to a user' s weighted search. The intent is to improve precision and/or recall. The additional terms may be taken from a thesaurus. For example a search for "car" may be expanded to: car cars auto autos automobile automobiles. The additional terms may also be taken from documents that the user has specified as being relevant this is the basis for the "more like this" feature of some search engines. The extra terms can have positive or negative weights. (1999-08-27)
