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THESAURUS

A thesaurus is a reference work that lists words grouped together according to similarity of meaning

containing synonyms and sometimes antonyms in contrast to a dictionary, which contains definitions

and pronunciations. The largest thesaurus in the world is the Historical Thesaurus of the Oxford English

Dictionary which contains more than 920,000 entries.

Although including synonyms, a thesaurus should not be taken as a complete list of all the synonyms for

a particular word. The entries are also designed for drawing distinctions between similar words and

assisting in choosing exactly the right word. Unlike a dictionary, a thesaurus entry does not give the

definition of words.

The word "thesaurus" is derived from 16th-century New Latin, in turn from Latinthsaurus, which is the

latinisation of the Greek literally "treasure store", generally meaning a collection of things which are of

big importance or value (and thus the medieval rank ofthesaurer was a synonym for treasurer). This

meaning has been largely supplanted by Roget's usage of the term.

In Information Science, Library Science, and Information Technology, specialized thesauri are designed

for information retrieval. They are a type ofcontrolled vocabulary, for indexing or tagging purposes.

Such a thesaurus can be used as the basis of an index for online material. The Art and Architecture

Thesaurus, for example, is used to index the Canadian Information retrieval thesauri are formally

organized so that existing relationships between concepts are made explicit. As a result, they are more

complex than simpler controlled vocabularies such as authority lists and synonym rings. Each term is

placed in context, allowing a user to distinguish between "bureau" the office and "bureau" the furniture.

Following international standards, they are generally arranged hierarchically by themes, topics or facets.

Unlike a literary thesaurus, these specialized thesauri typically focus on one discipline, subject or field of

study.

In information technology, a thesaurus represents a database or list of semantically orthogonal topical

search keys. In the field of Artificial Intelligence, a thesaurus may sometimes be referred to as an

ontology.

Thesauri for information retrieval are typically constructed by information specialists, and have their

own unique vocabulary defining different kinds of terms and relationships:

http://en.wikipedia.org/wiki/Reference_workhttp://en.wikipedia.org/wiki/Synonymshttp://en.wikipedia.org/wiki/Antonymshttp://en.wikipedia.org/wiki/Dictionaryhttp://en.wikipedia.org/wiki/Definitionshttp://en.wikipedia.org/wiki/Pronunciationshttp://en.wikipedia.org/wiki/Historical_Thesaurus_of_the_Oxford_English_Dictionaryhttp://en.wikipedia.org/wiki/Historical_Thesaurus_of_the_Oxford_English_Dictionaryhttp://en.wikipedia.org/wiki/Dictionaryhttp://en.wikipedia.org/wiki/New_Latinhttp://en.wikipedia.org/wiki/Latinhttp://en.wiktionary.org/wiki/en:thesaurus#Latinhttp://en.wiktionary.org/wiki/en:thesaurus#Latinhttp://en.wiktionary.org/wiki/en:thesaurus#Latinhttp://en.wiktionary.org/wiki/en:thesaurus#Latinhttp://en.wikipedia.org/wiki/Latinisation_(literature)http://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Treasurerhttp://en.wikipedia.org/wiki/Information_Sciencehttp://en.wikipedia.org/wiki/Library_Sciencehttp://en.wikipedia.org/wiki/Information_Technologyhttp://en.wikipedia.org/wiki/Controlled_vocabularyhttp://en.wikipedia.org/wiki/Art_and_Architecture_Thesaurushttp://en.wikipedia.org/wiki/Art_and_Architecture_Thesaurushttp://en.wikipedia.org/wiki/Synonym_ringhttp://en.wikipedia.org/wiki/Information_technologyhttp://en.wikipedia.org/wiki/Orthogonalhttp://en.wikipedia.org/wiki/Artificial_Intelligencehttp://en.wikipedia.org/wiki/Ontology_(information_science)http://en.wikipedia.org/wiki/Ontology_(information_science)http://en.wikipedia.org/wiki/Artificial_Intelligencehttp://en.wikipedia.org/wiki/Orthogonalhttp://en.wikipedia.org/wiki/Information_technologyhttp://en.wikipedia.org/wiki/Synonym_ringhttp://en.wikipedia.org/wiki/Art_and_Architecture_Thesaurushttp://en.wikipedia.org/wiki/Art_and_Architecture_Thesaurushttp://en.wikipedia.org/wiki/Controlled_vocabularyhttp://en.wikipedia.org/wiki/Information_Technologyhttp://en.wikipedia.org/wiki/Library_Sciencehttp://en.wikipedia.org/wiki/Information_Sciencehttp://en.wikipedia.org/wiki/Treasurerhttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Latinisation_(literature)http://en.wiktionary.org/wiki/en:thesaurus#Latinhttp://en.wikipedia.org/wiki/Latinhttp://en.wikipedia.org/wiki/New_Latinhttp://en.wikipedia.org/wiki/Dictionaryhttp://en.wikipedia.org/wiki/Historical_Thesaurus_of_the_Oxford_English_Dictionaryhttp://en.wikipedia.org/wiki/Historical_Thesaurus_of_the_Oxford_English_Dictionaryhttp://en.wikipedia.org/wiki/Pronunciationshttp://en.wikipedia.org/wiki/Definitionshttp://en.wikipedia.org/wiki/Dictionaryhttp://en.wikipedia.org/wiki/Antonymshttp://en.wikipedia.org/wiki/Synonymshttp://en.wikipedia.org/wiki/Reference_work

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Terms are the basic semantic units for conveying concepts. They are usually single-word nouns, since

nouns are the most concrete part of speech. Verbs can be converted to nouns "cleans" to "cleaning",

"reads" to "reading", and so on. Adjectives and adverbs, however, seldom convey any meaning useful

for indexing. When a term is ambiguous, a scope note can be added to ensure consistency, and give

direction on how to interpret the term. Not every term needs a scope note, but their presence is of

considerable help in using a thesaurus correctly and reaching a correct understanding of the given field

of knowledge.

"Term relationships" are links between terms. These relationships can be divided into three types:

hierarchical, equivalency or associative.

Hierarchicalrelationships are used to indicate terms which are narrower and broader in scope. A"Broader Term" (BT) or hyperonym is a more general term, e.g. Apparatus is a generalization

of Computers. Reciprocally, a Narrower Term (NT) or hyponym is a more specific term, e.g.

Digital Computer is a specialization of Computer. BT and NT are reciprocals; a broader term

necessarily implies at least one other term which is narrower. BT and NT are used to indicate

class relationships, as well as part-whole relationships (meronyms and holonyms).

The equivalency relationship is used primarily to connect synonyms and near-synonyms. Use(USE) and Used For (UF) indicators are used when an authorized term is to be used for another,

unauthorized, term; for example, the entry for the authorized term "Frequency" could have the

indicator "UF Pitch". Reciprocally, the entry for the unauthorized term "Pitch" would have the

indicator "USE Frequency". Unauthorized terms are often called "entry vocabulary", "entry

points", "lead-in terms", or "non-preferred terms", pointing to the authorized term (also

referred to as the Preferred Term or Descriptor) that has been chosen to stand for the concept.

As such, their presence in text can be used by automated indexing software to suggest the

Preferred Term being used as an Indexing Term.

Associative relationships are used to connect two related terms whose relationship is neitherhierarchical nor equivalent. This relationship is described by the indicator "Related Term" (RT).

Associative relationships should be applied with caution, since excessive use of RTs will reduce

specificity in searches. Consider the following: if the typical user is searching with term "A",

would they also want resources tagged with term "B"? If the answer is no, then an associative

relationship should not be established.

http://en.wikipedia.org/wiki/Terminologyhttp://en.wikipedia.org/wiki/Concepthttp://en.wikipedia.org/wiki/Nounhttp://en.wikipedia.org/wiki/Part_of_speechhttp://en.wikipedia.org/wiki/Ambiguityhttp://en.wikipedia.org/wiki/Ambiguityhttp://en.wikipedia.org/wiki/Hyperonymhttp://en.wikipedia.org/wiki/Hyponymhttp://en.wikipedia.org/wiki/Hyponymhttp://en.wikipedia.org/wiki/Meronymhttp://en.wikipedia.org/wiki/Holonymhttp://en.wikipedia.org/wiki/Holonymhttp://en.wikipedia.org/wiki/Meronymhttp://en.wikipedia.org/wiki/Hyponymhttp://en.wikipedia.org/wiki/Hyperonymhttp://en.wikipedia.org/wiki/Ambiguityhttp://en.wikipedia.org/wiki/Part_of_speechhttp://en.wikipedia.org/wiki/Nounhttp://en.wikipedia.org/wiki/Concepthttp://en.wikipedia.org/wiki/Terminology