Section 2 in The Standards of Weights and Measures (National Standards) Rules, 1988
2. Definitions
- In these rules, unless the context otherwise requires,--(a);"Act" means the Standards of Weights and Measures Act, 1976 (60 of 1976);(b);"coefficient" means those parameters without physical dimensions or ratios of quantities of the same kind, which are necessary for particular measurements or for characterising properties of substances or mixtures of certain substances.IllustrationDegree of alcoholic strength, percentage of sugar, and hardness of materials, are examples of coefficients;(c);"derived units" means units, expressed algebraically in terms of base units, or in terms of base and supplementary units of weights or measures, by means of mathematical symbols of multiplication or division, or both.Explanation I.- Derived units having special names and symbols (such as "newton", with symbol N') may, by themselves, be used to express other derived units in a simpler way than in terms of the base units of weights and measures.Explanation II.-The values of dimensionless quantities (such as refractive index, specific gravity, relative permeability or relative permittivity) are expressed by numbers. In such cases the corresponding unit shall be the ratio of the relevant two units and may be expressed by a number;(d);"International System of Units" of weights and measures means "Le System International d' Units", with the international abbreviation SI' established by the General Conference on Weights and Measures.Explanation.-SI' is divided into three classes of units, namely,--(i);base units, as defined in the Act;(ii);derived units; and(iii);supplementary units;(e);"permitted units" means the units which though not part of the SI, are recognised and permitted by the General Conference on Weights and Measures for general use along with SI units;(f);"physical constants" means those constants which express the value of physical invariants in a given system of units. These constants includes,--(i);those which correlate two or more physical quantities to express a physical phenomenon in quantitative terms independent of any material properties; for example, gravitational constant, velocity of light, etc.(ii);those which correlate the microscope properties of elementary particles (atoms, molecules, etc.) to the corresponding macroscopic properties; for example; Avogadro constant, Faraday constant, etc.(iii);those conversion factors used to express the same parameter in terms of inde-pendently defined units; for example, the conversion factor relating the astro-nomical unit or parasec to the metre and atomic mass unit to kilogram;(iv);those which describe the material properties of pure substances, for example, thermal conductivity, specific resistance, etc.(g);"Schedule" means Schedule appended to these rules;(h);"SI prefix" means the name and symbol of a prefix used for forming decimal multiples and sub-multiples of SI units, and of such other units as are permitted subject to any exception or modification by the General Conference on Weights and Measures or the International Organisation of Legal Metrology, or both, to be used along with the SI units;(i);"special units" means units, outside the SI, which are ordinarily used in specialised fields of scientific research. The values of those units expressed in SI units can only be obtained by experiment, and are, therefore, not known exactly.Explanation.-The value of electron volt (the unit of energy) depends upon the experimen-tally determined value of the charge of an electron;(j);"supplementary units" means the units of weight or measure which have been specified as such by the General Conference on Weights and Measures.Explanation.-Supplementary units may be used to form derived units;(k);"symbol" means a letter or a group of letters, written or combined in the specified manner for the convenient representation of a unit or a group of units;(l);"temporarily accepted units" means the units of weight or measure which have been recognised for the time being by the General Conference on Weights and Measures, for use along with SI units.
