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- Recommendation B.161)
- USE OF CERTAIN TERMS LINKED WITH PHYSICAL QUANTITIES
- The CCITT,
- considering
- (a) that ITU technical texts contain a number of terms expressing a
- relationship between quantities, such as quotient, ratio, coefficient, factor,
- index, constant, rate, etc., and that their meaning is liable to cause confusion
- owing to a lack of consistency;
- (b) that the situation is particularly confused owing to the existence of
- three working languages, as can be seen from such texts as the Provisional
- Glossary of Telecommunications Terms published by the ITU in 1979;
- (c) that attempts at standardization have been made in certain countries,
- in vocabularies recently prepared by the IEC and the JCG and in ISO International
- Standards,
- recommends
- (1) that certain terms linked with physical quantities should be used by
- authors and translators of ITU texts, according to the guidelines annexed to this
- Recommendation;
- (2) that these guidelines should be used to ensure that the term chosen to
- denote a quantity, fully describes its nature;
- (3) that these guidelines should be followed when forming new terms or
- reviewing existing terms which deviate from the guidelines.
- ANNEX A
- (to Recommendation B.16)
- Guidelines for the use in ITU texts of certain terms linked
- with physical quantities in French, English and Spanish
- A.1 Quotient
- The term "quotient" is used to express the result of the division of two
- numbers or two quantities. For example; when A/B = C, C is the quotient of A by
- B.
- This very general mathematical term is not used in the composition of the
- names of quantities, but does form part of the definition of some of them.
- In the context of definitions, quotient is a difficult word to use in
- English as it is often much more practical to use the expression "A divided by B"
- rather than "the quotient of A by B".
- Example: the pulse repetition frequency is the number of pulses in a pulse
- train divided by the duration of the pulse train.
- A.2 Coefficient and factor
- The words "coefficient" and "factor" are used for expressions representing
- the quotient of two quantities. They are used to form terms expressing certain
- quantities.
- A.2.1 Coefficient
- A
- A coefficient has therefore a dimension.
- Examples:
- Note: Table is missing
- The word ScoefficientT is also used in mathematics to express a number
- that multiplies the value of an algebraic quantity and in statistics (see ISO
- Standard 3534).
- Examples:
- Note: Table is missing
- A.2.2 Factor
- The word SfactorT is used when the two quantities are of the same kind. A
- factor is therefore dimensionless.
- Examples:
- Note: Table is missing
- A.3 Constant
- The term SconstantT should only be used to denote an invariable number or
- quantity.
- Examples: mathematical constants such as p, universal physical constants.
- Note: Table is missing
- The word SconstantT is sometimes used incorrectly, in conjunction with a
- qualifier, to indicate a variable characteristic quantity of a system or
- substance. In such cases, the use of the word is deprecated, and a specific term
-
- 1) A similar text will be submitted to the CCIR as a revision of Recommendation 663.
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- Fascicle I.3 - Rec. B.16 PAGE1
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- should be used (frequently the word ScoefficientT suitably qualified) or in
- French, in the absence of such a term, the word ScaractiristiqueT.
- Note: Table is missing
- However, the term Stime constantT (E), Sconstante de tempsT (F),
- Sconstante de tiempoT (S) is acceptable, as it is in common use.
- A.4 Index
- In French and Spanish the term SindiceT (F), SmndiceT (S) is sometimes
- used instead of SfacteurT (F), SfactorT (S). In English SindexT is sometimes used
- instead of SratioT in those cases where one of the two quantities is a reference
- quantity.
- Examples:
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- PAGE4 Fascicle I.3 - Rec. B.16
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- Note: Table is missing
- The term also designates a quantity which is not clearly defined or which
- is identifiable rather than measurable.
- Example:
- Note: Table is missing
- In all the above cases extension of the usage of the term is not
- recommended. It should be replaced wherever possible by the terms coefficient,
- factor or (in English) ratio, or by a specific term of magnitude. Thus the French
- term "L'indice de force des sons" was replaced by "l'affaiblissement pour la
- sonie", "loudness rating" (E), "coeficiente de sonoridad" (S).
- A.5 Ratio
- The term "ratio" is used to express the result of the division of two
- numbers or two quantities of the same kind. It may therefore be used in this case
- as an equivalent of the term "quotient".
- Examples:
- - Attenuation is defined as the ratio of two powers.
- - Ratio of A to B.
- - Ratio of width to height (picture).
- In English and in Spanish, the word "ratio" ("relación") is also used to
- explicitly indicate the fractional expression of the relationship between two
- quantities before the division is performed, e.g. written as a fraction or a
- relationship as 5/21 or 5 : 21 rather than the resulting 0.238. The two
- quantities may or may not be the same, e.g. power/weight ratio, relación
- potencia/peso.
- In French and in Spanish the term "rapport" (F) ("relación" (S)) should
- not be used when the two quantities are not the same physical kind, or when they
- are of a different mathematical kind, for example, to express the quotient of a
- vector or a tensor by a scalar number.
- The word is also used to form terms for expressing dimensionless
- quantities.
- Examples:
- Note: Table is missing
- Note - Error ration is normally expressed as a decimal fraction, e.g. 4 .
- 10-5.
- A.6 Rate, ratio (E); Taux, débit (F); Tasa/proporción/frecuencia (S)
- reliabi
- reliability.
- Although in English the term SrateT may be used to express the
- relationship between two quantities of the same kind, it is generally used to
- express the relationship of quantities of a different kind (particulaarly a
- quantity per unit of time). For expressing the proportion of errors in
- telecommunication however, the use of this term can be confusing and is
- deprecated. The term SratioT should be used for this purpose.
- In Spanish, the term StasaT should not be used to express the relationship
- between a quantity and the unit of time. There are a number of different terms
- which should be used for this purpose depending on the quantity e.g. SvelocidadT
- (S) for distance, SfrecuenciaT (S) for events, ScaudalT (S) for volume flow, etc.
- In Spanish, the term StasaT is also frequently used incorrectly to
- indicate a factor or index usually expressed as a percentage or in hundredths or
- as a smaller decimal fraction such as a thousandth or millionth. The use of this
- erm for this term for this purpose in Spanish is deprecated and should be
- replaced by the term SproporcisnT (S).
- Examples:
- Note: Table is missing
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- Fascicle I.3 - Rec. B.16 PAGE1
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