One useful feature might be a special character in the search term which means "but ignore": for example. when searching the art gallery for "diver" (for underwater scenes), the searcher also picked up "divert" and "diversion" and "diverse" and "Sir Bedivere". Another feature is the exclude term. They can be used in the Alta Vista web searcher, where a minus sign as a prefix means "do not list any web page that contains this word". An example is, if someone is looking for information about jaguars (the animal), but does not want to be swamped in references to Jaguar Cars.