retardation
(riːtɑːˈdeɪʃən)
Also 5 retardacion, -acioun, -acyoun.
[a. F. retardation, † -acion (14th c., = Sp. retardacion, It. -azione), or ad. L. retardātiōn-em, n. of action f. retardāre to retard.]
1. a. The action of retarding, delaying, or making slower in respect of action or movement, or later in happening; an instance of this.
| 1426 Lydg. De Guil. Pilgrim. 12362 Sythe thys bodyes celestyal..Ben let thus in ther mocyouns, And han swych retardacyouns. 1472–5 Rolls of Parlt. VI. 161/1 To grete delay and retardation of procedyng. 1508 in Lett. Rich. III & Hen. VII (Rolls) I. 451 The retardacion of their ambassade. 1513 Hen. VIII in Strype Eccl. Mem. (1822) I. ii. 6 By the retardation of our said ship she now lately fell into the daungier & hands of the Mores. 1597 I. T. Serm. Paules Crosse 66 Retardation of death, of this saith Ezechiel, I will not the death of a sinner, but rather that hee turne and liue. 1605 Bacon Adv. Learn. ii. xv. §1 Causing a retardation of reading, and some sloth or relaxation of memory. 1661 Cowley College, All manner of Experiments concerning Plants, as their Melioration, Acceleration, Retardation. 1702 C. Mather Magn. Chr. i. ii. (1852) 46 Finding the Reformation of the Church..to labour under a sort of hopeless retardation. 1759 B. Stillingfleet Misc. Tracts (1762) 253 In order to determine accurately the acceleration or retardation of the winter. 1817 Malthus Popul. (ed. 4) III. 421 A gradual change..would then effect the necessary retardation in the rate of increase. 1865 C. J. Ellicott Destiny of Creature Pref. 6 They speak of nought but obstructions and retardations, where all is buoyancy and progress. 1891 C. L. Morgan Anim. Life & Intell. 223 This retardation or decreased rate of growth. |
† b. Lingering or staying behind. Obs. rare—1.
| 1633 T. Adams Expos. 2 Peter iii. 18 Think upon his [Lot's] wife's retardation and retrospection. |
2. In the physical sciences in various special applications: a. of motion or moving bodies. (Opposed to acceleration.)
| 1642 H. More Song of Soul Notes, Wks. (Grosart) 152/1 The acceleration or retardation of the motion of the Earth will make the sea fluctuate. 1665 Phil. Trans. I. 106 The cause of this acceleration and retardation of their true Motion. 1727–38 Chambers Cycl. s.v., The retardation of moving bodies arises from two great causes, the resistence of the medium, and the force of gravity. 1794 G. Adams Nat. & Exp. Philos. III. xxvii. 119 Accelerations and retardations may be considered as quantities, and are measured by the changes of velocity. 1825 J. Nicholson Operat. Mechanic 3 From a clear comprehension of the acceleration of motion in bodies the retardation of motion will be easily conceived. 1862 Spencer First Princ. ii. v. §56 (1875) 182 In an elliptical orbit there is now acceleration and now retardation. 1878 Huxley Physiogr. 172 The retardation of the deeper part of the wave by friction against the sea bottom. |
b. of the tides: (a) The excess of periods of high water above the solar day. (b) = retard n. 2.
| 1797 Encycl. Brit. (ed. 3) XVIII. 521/1 The difference between a solar day and a tide day is called the priming or the retardation of the tides. 1845 Encycl. Metrop. V. 241* The average retardation from day to day being about 40 minutes. Ibid. 257* The retardation of high water after the moon's passage over the meridian. 1888 Encycl. Brit. XXIII. 366/2 When the mean semi-range and retardation of any tide are known its height may be computed for any instant. |
c. of celestial bodies. (Cf. quot. 1426 in 1.)
| 1812–16 Playfair Nat. Phil. (1819) II. 183 The amount of the retardation, from the opposition to the conjunction, is 16{supm} 26s nearly. 1849 Herschel Outl. Astron. §683 Over quadrant AD, approach and retardation, therefore advance of apsides. 1873 Proctor Moon 93 Retardation ceases to act when the moon is at M2. |
d. of rays or waves of light, heat, etc.
| 1831 Brewster Optics xxiv. 213 They will..produce a colour or a fringe corresponding to the retardation of one of the rays within the plate. 1866 R. M. Ferguson Electr. (1870) 245 The retardation increases with the square of the length of the line. 1882 Minchin Unipl. Kinemat. 18 A retardation of a whole wave length..is tantamount to no retardation at all. |
3. Music. a. (See quots. 1868 and 1899.)
| 1818 Busby Gram. Mus. 339 This Discord, the dissonant note of which is but a retardation of the Eighth, is liable to four changes. 1868 Ouseley Harmony ix, When an interval of a melody (or of an inner part) is kept back in ascending, it is called a retardation. 1899 Bridge & Sawyer Harmony xiii, A Retardation is formed when a note, which should ascend in its progression one degree, is delayed. |
b. A slackening of the tempo.
| 1834 [see a tempo]. 1853 Charles Auchester II. 180 The slightest possible retardation at its close brought us to the refrain of the simple adagio. |
4. Psychol. Educational progress which is slower than average for the age-group; also, mental backwardness or subnormality in an adult. Cf. retarded ppl. a. 1 b.
| 1907 Psychol. Clinic I. 98 The failure of many pupils to be promoted regularly from grade to grade—retardation—has been a subject for..serious consideration. 1914 W. B. Drummond tr. Binet & Simon's Mentally Defective Children ii. 16 According to a convention..we regard as defective in intelligence a child who shows a retardation of three years, when he himself is nine years of age or more. 1919 L. M. Terman Measurement of Intelligence i. 4 We can at least prevent the kind of retardation which involves failure and the repetition of a school grade. 1937 C. L. Burt Backward Child iv. 78 Thus, at the age of 10, the borderline for backwardness is a retardation of 1½ years (not, as is so commonly stated, of 2 years), or, in terms of the ratio, 15 per cent. 1963 N. R. Ellis Handbk. Mental Deficiency xxi. 678 Skill areas listed from most to least retardation were reading, arithmetic, writing, and spelling. 1970 Hinsie & Campbell Psychiatric Dict. (ed. 4) 666/1 Fashions in labeling this group change almost from year to year; in the 1960's, mental retardation was the favorite appellation, and justifiably so in that it does not imply that inheritance or constitutional defects are always the cause of mental retardation. 1975 Balthazar & Stevens Emotionally Disturbed, Mentally Retarded i. 3 The problems imposed by mental retardation and adaptive behavior. |