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proportionality|prəʊpɔəʃəˈnælɪtɪ|
[ad. F. proportionnalité (14th c. in Littré), or ad. med.L. prōportiōnālitās, -tātem (Scotus Erigena, 875): see proportional and -ity.]
1. a. The quality, character, or fact of being proportional.
1569J. Sandford tr. Agrippa's Van. Artes 25 b, In like manner of proportion and proportionallitie, and of their species. 1701Grew Cosm. Sacra ii. ii. §5. 37 All Sense, so far as Grateful, dependeth upon the Equality, or the Proportionality, of the Motion or Impression which is made. 1830Herschel Stud. Nat. Phil. 152 Proportionality of the effect to its cause. 1854Scoffern in Orr's Circ. Sc., Chem. 31 Definite proportionality [i.e. the fact of combining in definite proportions] may be said to be the..characteristic of chemical combinations.
b. limit of proportionality (Mech.) = proportional limit.
1888W. C. Unwin Testing of Materials of Construction iii. 65 Between A and B a sensible, but slight, curvature appears in the diagram, and a sensible, though small, deviation from proportionality begins to appear in the stresses and strains. Bauschinger calls the point A the limit of proportionality. 1930Engineering 3 Jan. 31/1 The figures for limit of proportionality..were obtained from stress-strain diagrams. 1971B. Scharf Engin. & its Lang. iv. 22 The following values may be obtained by means of a tensile test: limit of proportionality..; yield stress..; proof stress [etc.].
c. constant or factor of proportionality (also proportionality constant, proportionality factor): the constant ratio of one variable to a second to which it is proportional.
1919Smithsonian Misc. Coll. LXXI. ii. 9 The cross section, S, should obviously be as small as possible; and this condition will be satisfied at all times, provided it is the following function of the mass of the rocket (M - m), S = A (M - m)2/3, where A is a constant of proportionality. 1937Rev. Sci. Instruments VIII. 255/1 These are all connected with..proportionality between resultant electrical impulse and initial ionization per particle. The proportionality factor should not depend much upon the kind of particle entering the counter. 1955J. Lindhard in W. Pauli Niels Bohr 188 Accordingly, ω and the average excitation potential become proportional to Z, i.e. ℏω = I = Z.I0. However, it was found difficult to calculate the proportionality constant I0. 1962F. I. Ordway et al. Basic Astronautics x. 396 The proportionality factor CF, called thrust coefficient, is a result of the expansion of the combustion gases through the nozzle.
2. A formula affirming the proportionality of two or more quantities.
1954A. Dresden tr. van der Waerden's Science Awakening vi. 176 The proportionality a:b::c:a means that na>mb implies nc>md, and na = mb implies nc = md, and na7M5 ∝ t3. |