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parameter Math.|pəˈræmɪtə(r)|
[a. mod.L. parameter, -metrum, fem. (Mydorge 1631), in F. paramètre (‘la ligne nommé ailleurs costé droit, paramètre, et icy coadjuteur’ Desargues 1639); f. Gr. παρα- beside, subsidiary to + µέτρον measure.]
1. In conic sections: The third proportional to any given diameter and its conjugate (or, in the parabola, to any abscissa on a given diameter and the corresponding ordinate); this is the parameter of the given diameter. spec. The parameter of the transverse axis (principal parameter, or parameter of the curve), i.e. the latus rectum, or focal chord perpendicular to the axis.[1631C. Mydorge Prodrom. Catopt. & Diopt. siue Conicorum 3 Def. xix, Parametrum coni sectionis dicimus, rectam lineam à cuiuslibet coni sectionis, aut portionis, vertice eductam ordinatim ad contiguam diametrum applicatis æquidistantem... Quæ, si ab axis termino sit educta, recta parameter..dicetur.] 1656Hobbes Six Lessons Wks. 1845 VII. 259 As much in vain..as seek for the focus or parameter of the parabola of Dives and Lazarus. 1704J. Harris Lex. Techn. I, Parameter, by some..called the Latus Rectum of a Parabola, is a Third Proportional to the Abscissa and any Ordinate. 1795Hutton Math. Dict., Parameter, a certain constant right line in each of the three Conic Sections; otherwise called also Latus Rectum..; being..a third proportional to the transverse and conjugate axes, in the ellipse and hyperbola; and, which is the same thing, a third proportional to any absciss and its ordinate in the parabola. 1798― Course Math. (1811) II. 123 The Parameter of any Diameter [of a parabola] is equal to four Times the Line drawn from the Focus to the Vertex of that Diameter. 1816tr. Lacroix's Diff. & Int. Calculus 401 If..the parameter of a parabola be made to vary, a series of parabolas will be obtained. 1891C. Taylor Elem. Geom. Conics (ed. 7) iii. §17 The Parameter of any diameter of a parabola is the focal chord which it bisects: thus the latus rectum is the parameter of the axis.
2. a. gen. A quantity which is constant (as distinct from the ordinary variables) in a particular case considered, but which varies in different cases; esp. a constant occurring in the equation of a curve or surface, by the variation of which the equation is made to represent a family of such curves or surfaces (cf. quot. 1816 in 1); also in Computing.
1852B. Price Infinites. Calc. I. xiii. 409 If an equation to a curve be given, involving one or more constants, as well as the current coordinates, the position and dimensions of the curve will be changed by a change in the constants, and yet the class may remain the same... A constant that enters into an equation, and varies in the way above explained, is called a variable parameter. 1859Parkinson Optics (1866) 4 The refractive index between the two media..is a parameter which varies, (i) if the nature of the light be altered, (ii) if the relation between the two media be altered. 1879Thomson & Tait Nat. Phil. I. i. §293. 1885 C. Leudesdorf Cremona's Proj. Geom. 63 This anharmonic ratio is called the coefficient or parameter of the homology. 1954Computers & Automation Dec. 18/1 Parameter, in a subroutine, a quantity which may be given different values when the subroutine is used in different parts of one main routine, but which usually remains unchanged throughout any one such use. 1958Communications (Assoc. Computing Machinery) Dec. 16 A procedure..is a closed and self-contained process with a fixed ordered set of input and output parameters. 1965[see keyboarded ppl. adj. s.v. keyboard v.]. 1969Computers & Humanities III. 278 Thus input parameters were included to specify page width and length, and the dictionary was photo⁓offset. 1973C. W. Gear Introd. Computer Sci. v. 201 A and B are input parameters, so they can be given values by any expression when the subroutine is called. 1973Murrill & Smith Introd. Computer Sci. 585 Through the use of arguments and parameters, subroutines and functions can be used throughout a program to perform identical operations upon many different data items.
b. Astron. = element 7 a.
1829Encycl. Metrop. Div. 2 I. Index, Variation of Parameters. [Ibid. 699 Variation of elements of orbit.] 1840Penny Cycl. XVII. 240/1 The parameters of the orbits are now generally called their elements. 1841Proc. Amer. Phil. Soc. II. 19 Orbits having small parameters. 1963R. H. Merson in M. Roy Dynamics of Satellites 83 The values of the six basic elements at a given time..are determined from a set of observations by a differential correction technique... In addition to the estimates of the orbital parameters, estimates of their variances and covariances are also determined. 1967Technology Week 20 Feb. 13 Orbital parameters were apogee—817·2 mi.; perigee—128 mi.; inclination—48·4 degrees, and period 100·3 minutes. 1975Nature 18 Sept. 184/2 Even though a few comets with hyperbolic orbits have been seen, Whipple's calculations show that for four candidates—the only ones..with well determined parameters—the chance of any one having arrived on such an orbit from interstellar space is less than 1 in 104.
c. Cryst. Each of the intercepts made upon the axes in a crystal by the plane which is chosen for a face of the unit or primary pyramid.
1839W. H. Miller Crystallogr. 2 The parameters are the portions of the axes cut off by a given face. 1878Gurney Crystallogr. 18, a, b, c the parameters of the crystal. 1895Story-Maskelyne Crystallogr. ii. §18 The ratios a:b:c of the intercepts [on the axes] of some one plane chosen as a standard or parametral plane are termed the parametral ratios or parameters of the system as referred to the axes X, Y, Z.
d. Math. An independent variable in terms of which each co-ordinate of a point is expressed, independently of the other co-ordinates.
1873G. Salmon Treat. Higher Plane Curves (ed. 2) viii. 317 The coordinates x′, y′, z′ are..expressible as quadric functions of a parameter θ. 1907Grace & Rosenberg Coordinate Geom. xvi. 220 If we can find simple expressions for the coordinates of points on a conic in terms of one variable quantity, a point on the curve may be looked on as determined by a definite value of the variable, the variable being usually called the parameter. 1937Michell & Belz Elem. Math. Analysis I. vii. 401 Taking x2/a2 - y2/b2 = 1, (a, b positive), as the equation of the hyperbola, we can evidently write x = {pm}a cosh ϕ, y = b sinh ϕ, introducing ϕ as parameter. 1969J. J. Stoker Differential Geom. iv. 75 As with curves, the surface parameters are to a considerable degree arbitrary; in fact, parameters u, v can be replaced by new parameters through the equations u = ϕ1(u, v), v = ϕ2(u, v), provided that the Jacobian ∂( u, v )/(u, v) is different from zero.
e. Electr. Any of several numerical quantities that can be used jointly to characterize a network.
1911Trans. Amer. Inst. Electr. Engin. XXX. 885 The impedances required to make a normal type of network of the requisite number of parameters equivalent to the given network under specified conditions of operation. 1930T. E. Shea Transmission Networks & Wave Filters iii. 71 Any network having one pair of input and one pair of output terminals may be completely represented..by a T network (or network having any form providing at least three independent parameters) as far as external current and voltage conditions are concerned. 1962Simpson & Richards Physical Princ. Junction Transistors v. 82 The h's define the following circuit parameters: h11 = hi = input impedance with output short-circuited.., h12 = hr = reverse voltage ratio with input open-circuited. 1966R. H. Mattson Electronics ix. 381 The y parameters are used when discussing feedback amplifiers and pentode amplifiers. The h parameters are used when discussing transistor circuits.
f. Statistics. A numerical characteristic of a population (as distinguished from a ‘statistic’, which relates to a sample).
1922R. A. Fisher in Phil. Trans. R. Soc. A. CCXXII. 311 The law of distribution of this hypothetical population is specified by relatively few parameters. Ibid. 313 These involve the choice of methods of calculating from a sample statistical derivates, or as we shall call them statistics, which are designed to estimate the values of the parameters of the hypothetical population. 1939A. E. Treloar Elem. Statistical Reasoning x. 130 The true sampling error of each sample mean and standard deviation, so far as those statistics form estimates of the corresponding parameters, may be expressed as [etc.]. 1962E. S. Keeping Introd. Statistical Inference v. 95 If..the population is assumed to be normal, as far as a particular variate is concerned, the density function for this variate will contain two parameters, µ and σ, which are the population mean and standard deviation respectively. 1975Harnett & Murphy Introd. Statistical Anal. i. 5 The numerical characteristics of a sample are used to estimate the parameters of the parent population from which this sample was drawn. A numerical characteristic used for this purpose is referred to as a sample statistic, or usually just a statistic.
3. In extended use: any distinguishing or defining characteristic or feature, esp. one that may be measured or quantified; an element or aspect of anything; loosely, a boundary or limit.
1927Proc. R. Soc. A. CXIII. 642 In the case of phenacite, the symmetry of the structure imposes no limitations on the position of the seven atoms in the molecule, so that twenty-one parameters are required to define the structure. 1934Ibid. CXLVI. 570 Few of the structures of hydrated salts have as yet been found. This may be due to the large numbers of parameters usually involved, which, in the absence of any general laws concerning water of crystallization, makes the analysis very difficult. 1939Brevoort & Joyner Cooling on Front of Air-Cooled Engine Cylinder (NACA Techn. Rep. No. 674) 1/1 These results are introductory to the study of front cooling and show the general effect of the several test parameters. 1950J. C. Slater Microwave Electronics x. 230 The quantity, x..occurs frequently in klystron theory and is called the bunching parameter. 1957Times 11 Sept. 6/2 The principle that it was possible to specify the sounds of speech in terms of six parameters or factors, which might be considered as functions of time. 1961Jrnl. Speech & Hearing Res. IV. 10/1 There is some evidence..that parameters other than the formant frequencies may influence human judgement of vowel qualities. 1962Rep. Comm. Broadcasting 1960 335 in Parl. Papers 1961–2 (Cmnd. 1753) IX. 259 Many Western European countries..are considering whether there would be advantage in using..the technical parameters they already use for 625-line standards in the 7 Mc/s channels of Bands I and III. 1964A. Edel in I. L. Horowitz New Sociol. xiv. 220 A theory of human society is seen to involve a specific picture of the nature of man. We would then say that a social theory has a human-nature parameter. 1965Listener 9 Dec. 943/2 There remains the bulk of those for whom politics is a parameter of life rather like the weather. 1967Economist 16 Dec. 1157/1 A second, even bigger generator of 1,300 MW was also contracted for... With these orders, practically every existing parameter of power generating practice has been exceeded. 1970Time 3 Aug. 9 The fact that Nixon was willing to make his chastisement public suggests..that the President at least understands ‘the parameters of the problem’. 1971Jrnl. Gen. Psychol. LXXXIV. 18 Three phenomena corresponding to the three major parameters of color—brightness, hue, and saturation. 1972Nature 18 Feb. 373/2 In Fig. 2 ozone and radon concentrations together with various meteorological parameters are shown for two consecutive Saturdays. 1973N.Y. Times Mag. 25 Feb. 71/4 It carries, to begin with, the liberal presumption that the mind of man can in fact comprehend the major parameters of the world we inhabit. 1975D. M. Davin Closing Times p. xviii, There are parameters to these recollections which may not be immediately apparent: the world of learning..and the war... My chief parameter, however, is that of art. 1975Times 14 Oct. 15/4 The considerable element of indeterminacy which exists within the parameters of the parole system. 1975Publishers Weekly 27 Oct. 20/1 One disappointment for the publishers is that it [sc. the High Court decision] fails to provide any clear guidelines on the larger issue of the parameters of Government secrecy. 1976Listener 30 Sept. 419/3 Carter, who has made the running so far by raising the debate beyond the orthodox economic and financial political parameters. 1976H. Young Crossman Affair i. 19 At this meeting a word was first spoken and a concept first articulated which later came to dominate the Crossman Diaries case. The word was ‘parameters’... Sir John Hunt, in giving guidance on the limits within which an edited version of Crossman would have to be prepared, now formalized into a set of rules his interpretation of past practice... These parameters, or limits, excluded four particular areas from detailed report or discussion. |