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.
Fascicle I.3 - Rec. B.16 PAGE1
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:
PAGE4 Fascicle I.3 - Rec. B.16
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" ("relaci¢n") 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, relaci¢n
potencia/peso.
In French and in Spanish the term "rapport" (F) ("relaci¢n" (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, d‚bit (F); Tasa/proporci¢n/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
Fascicle I.3 - Rec. B.16 PAGE1