VII. Definition of Equivalence and Degrees of Equivalence [15]

As the standards for thesaurus construction acknowledge and the experience of theAAT residencies has confirmed, terms selected from more than one natural languagevary in the extent to which they represent the same concepts. These variationscan be seen as forming a continuum that ranges from exact matches or equivalencein meaning through partial or inexact equivalence to complete incompatibility ornon-equivalence.

  1. Exact equivalence: The target language contains a term that is: a)identical in meaning and scope to the term in the source language; and b) capableof functioning as a preferred indexing term in the target language. These termscan be described as equivalent. On the AAT bilingual term sheet and themultilingual term tracking sheet the degree of equivalence is marked as "=" (e.g. , rosary = rosaire = salterio).

  2. Inexact equivalence: A term in the target language expresses thesame general concept as the source language term, although the meanings of theseterms are not precisely identical. Put another way, one may say that the termis one language denotes the same set of objects in another language, but the"membership" of the set may be slightly different or take a slightly differentform. The AAT bilingual term sheet and multilingual term tracking sheetdesignate these matches as "+/-" (more or less). ISO 5964 states that althoughexact equivalence is not found, the terms represent the same general concept andmay be seen as more or less equal in multilingual thesaurus development (e. g., temple paien +/- ancient temple; atelier de fabrication+/- workshop; belvédère +/- gazebo).

  3. Partial equivalence: The term in the source language cannot bematched by an exactly equivalent term in the target language, but a neartranslation can be achieved by selecting a term with a slightly broader ornarrower meaning. The AAT bilingual term sheet and the multilingual termtracking sheet indicate these terms with ">" if the meaning of the term in thesource language is broader, or with "<" if it is narrower (e. g. ,agenouilloir = kneeler < inginocchiatoio).

  4. Single-to-multiple equivalence: The concept in the source languageis not recognized as a single term in the target language, but the concept towhich the source language term refers can be expressed by two or more existingpreferred terms in the target language. In some cases the term expresses acompound concept that might exist as more than one single descriptor in athesaurus like the AAT but is precoordinated in other languages. This degree ofequivalence is marked on the AAT bilingual term sheet and the multilingual termtracking sheet as "_+_. " (e. g. , ardoisière = slate + quarry).

  5. Non-equivalence: The target language does not contain a term thatcorresponds in meaning, either partially or inexactly, to the source language (e.g. , chaise à prie-Dieu = sedia inginocchiatoio = NE [in English]). Non-equivalence often occurs if one or more of the vocabularies used arenarrower in scope than the other vocabularies. In this case non-equivalence maybe replaced by adopting a loan term (refer to Section XI on loan and coined termsbelow). On the AAT bilingual term sheet and the multilingual term trackingsheet this degree of equivalence is marked as "X. " On the AAT bilingual termsheet the box "NO target equivalent" or "NO source equivalent" is also marked.

In some cases, as in the project to construct a multilingual thesaurus ofreligious objects, the participants decided not to use the "no-equivalent"designation for any term, since it was deemed imperative for access purposes fora name to be given to each object represented regardless of whether a name forthe object existed in each language. In these cases, it was decided to useeither loan or coined terms, depending on usage or felicity of phrasing for theconcept (see Section XI below).

15. This section is based on ISO 5964-1985 (E), pp. 8-9.