Information retrieval thesauri are formally organized so that existing relationships between concepts are made clear. For example, “citrus fruits” might be linked to the broader concept of “fruits”, and the narrower ones of “oranges”, “lemons”, etc. When the terms are displayed online, the links between them make it very easy to surf around the thesaurus, selecting useful terms for a search. When a single term could have more than one meaning, like tables (furniture) or tables (data), these are listed separately so that the user can choose which concept to search for and avoid retrieving irrelevant results. For any one concept, all the known synonyms are listed, such as “mad cow disease”, “bovine spongiform encephalopathy”, “BSE”, etc. The idea is to guide all the indexers and all the searchers to use the same term for the same concept, so that search results will be as complete as possible. If the thesaurus is multilingual, equivalent terms in other languages are shown too. Following international standards, concepts are generally arranged hierarchically within facets or grouped by themes or topics. Unlike a general thesaurus used for literary purposes, information retrieval thesauri typically focus on one discipline, subject or field of study.