▪ I. surd, a. and n.
(sɜːd)
Also 6–7 surde.
[ad. L. surdus (in active sense) deaf, (in pass. sense) silent, mute, dumb, (of sound, etc.) dull, indistinct.
The mathematical sense ‘irrational’ arises from L. surdus being used to render Gr. ἄλογος (Euclid bk. x. Def.), app. through the medium of Arab. a{cced}amm deaf, as in jaðr a{cced}amm surd root.]
A. adj.
1. Math. Of a number or quantity (esp. a root): That cannot be expressed in finite terms of ordinary numbers or quantities: = irrational A. 3. (Cf. incommensurable 1.) (See also quots.)
| 1551 Recorde Pathw. Knowl. ii. Pref., Quantitees partly rationall, and partly surde. 1571 Digges Pantom. iv. vi. X ij, Tetraedrons side being rationall, the Axis is surde, and it beareth proportion to the side as 1. to √ 24. 1623 Bp. Andrewes XCVI Serm. xvi. (1629) 156 Such surd numbers, such fractions we shall meet with, we shall not tell how or when to gett through. 1659 Leybourn Arith. iv. iv. (1660) 339 There are many sorts of surd roots, some are simple,..others are compound. 1798 Hutton Course Math. (1806) I. 80 The cube root of 8 is rational, being equal to 2; but the cube root of 9 is surd or irrational. 1861 T. Lund J. Wood's Elem. Alg. 97 An equation may be cleared of a surd by transposing the terms so that the surd shall form one side, and the rational quantities the other, and then raising both sides to that power which will rationalize the surd. 1908 G. H. Hardy Course Pure Math. i. 7 If a is a rational number, the two numbers {pm} √ a are either rational or irrational, and..generally the latter. Numbers of this kind, when irrational, are called pure quadratic surds. A number a {pm} √ b..is sometimes called a mixed quadratic surd. 1959 G. & R. C. James Math. Dict. 379/2 Surd, a sum of one or more irrational indicated roots of numbers. Sometimes used for irrational number. 1962 H. Cohn Second Course in Number Theory iii. 40 If a, b, c are integers..we define the conjugate surds λ = (a + b √ D)/c, λ{p} = (a - b √ D)/c. |
† 2. Deaf. Obs. rare.
| 1682 Sir T. Browne Chr. Mor. iii. §6 He..may..apprehend how all Words fall to the Ground, spent upon such a surd and Earless Generation of Men. 1819 H. Busk Vestriad i. 763 Whistlings, whizzes, strike thy senses surd. |
3. fig. † a. Not endowed with sense or perception; insensate, unintelligent. Obs.
In quot. 1668, deficient in perception, dull: cf. c.
| 1601 Holland Pliny xxvii. xiii. II. 292 Those medicinable vertues..bestowed vpon those surd and senslesse hearbs. 1668 H. More Div. Dial. ii. xxvi. (1713) 174 My palate is something more surd and jacent. a 1676 Hale Prim. Orig. Man. i. ii. (1677) 44 Neither Chance nor surd or inanimate Nature could be the Efficient of such a Being. |
b. Irrational, senseless, stupid. (In recent use only as a direct figure from 1.)
| 1610 A. Cooke Pope Joan 60 Rupertus,..commonly called Grosthead. A great Philosopher..though it pleased your Pope Innocentius the fourth, to call him old foole, surd, and absurd companion. 1625 Jackson Creed v. xlvii. §6 Their irrational and surd conceits of scripture's sense. 1642 H. More Song of Soul ii. i. i. vii, And foul blasphemous belch from their surd mouth resounds. |
| 1863 M. Pattison Ess. xvii. (1889) II. 295 The surd and irrational complexion of that party is due to the circumstance that all its best minds went from it. 1891 H. Jones Browning as Teacher 24 The problems have a surd or irrational element in them. |
† c. Not clearly or keenly perceived, dull; stingless. Obs.
| 1597 A. M. tr. Guillemeau's Fr. Chirurg. 48/2 The dolour not so pungent and sharp, but somwhat more surde and benumde. 1599 ― tr. Gabelhouer's Bk. Physicke 202/2 Take..oyle of Hempeseede and surde nettles. |
† d. Conveying no sense, meaningless. Obs.
| 1605 Bacon Adv. Learn. ii. xxv. §4 The Ceremonies of Idolatrie and Magicke that are full of Non-significants and surde characters. |
4. Phonetics. Uttered without vibration of the vocal cords; voiceless, ‘breathed’: opposed to sonant. (Cf. F. sourd.)
| 1767 Ess. in Ann. Reg. 194/1 Mute, surd, and nasal syllables. 1773 W. Kenrick Dict., Gram. Eng. Lang. 27 All our modes of articulation, whether surd or vocal. 1863 Max Müller Sci. Lang. Ser. ii. vii. (1868) 297 No longer mere interjections..uncertain between surd, sonant, or aspirated enunciation. 1887 Cook tr. Sievers' O.E. Gram. 99 P is a surd labial stop. |
5. Arabic Gram. (tr. Arab. a{cced}amm lit. deaf). Applied to verbs in which the second and third letters of the root are the same.
| 1776 Richardson Gram. Arab. Lang. iii. v. 97 The Surd verb, so called because the last radical is not heard, coalescing with the second by Teshdid. 1777 ― Arab.-Pers. Dict. 138 el' asammu The surd or teshdid conjugation of Arabick verbs. 1823 W. Price Gram. 3 Oriental Langs. 112 Conjugation of the Surd Verb, della, he ogled. |
B. n.
1. Math. A surd or irrational number or quantity, esp. root: see A. 1.
| 1557 Recorde Whetst. L l iij, Those nombers are not Surde nombers properly, but sette like Surdes. As the Square roote of .4. 1571 Digges Pantom. iv. vii. X ij b, The Hexaedrons comprehending Spheres Dimetiente beeing rationall, his Axis is a surde. 1674 S. Jeake Arith. (1696) 294 Surdes are Simple or Compound, Integral or Fracted. 1743 Emerson Fluxions 83 Any Power of the Quantity under the Vinculum (in any Binomial or Trinomial Surd). 1869 ‘Lewis Carroll’ Phantasmagoria 110 Yet what are all such gaieties to me Whose thoughts are full of indices and surds? |
| attrib. 1869 J. H. Smith Elem. Algebra 164 Surds of the same order are those for which the root-symbol or surd-index is the same. |
| fig. 1856 Ferrier Inst. Metaph. iv. (ed. 2) 143 It becomes the absolutely incogitable—a surd. 1877 E. Caird Philos. Kant ii. xv. 551 The old difficulty..that reappears always as the inexplicable surd of his philosophy. |
2. Phonetics. A speech-sound uttered without ‘voice’; a ‘breath’ consonant: see A. 4.
| 1789 E. Darwin Bot. Gard. II. 60 Weighs with nice ear the vowel, liquid, surd, And breaks in syllables the volant word. 1842 Proc. Philol. Soc. I. 7 The tenues (otherwise surds, or whisper-letters). 1871 Public Sch. Lat. Gram. 7 The use of C as a surd made K superfluous. |
▪ II. † surd, v.1 Obs.
[Repr. OE. *seordan: see sard v.]
trans. To defile.
| a 1400 Leg. Rood (1871) 143, I sauh my child ben surded and soyled. |
▪ III. surd, v.2
[f. L. surdus: see surd a.]
trans. To deaden or dull the sound of, as by a ‘sordine’ or mute. Also ˈsurding vbl. n. used attrib.
| 1625 Lisle Du Bartas, Noe Ded. ¶¶j b, To surd it, as young trompeters are wont. 1885 Encycl. Brit. XIX. 70/2 A surding or muting effect produced by impeding the vibration of the strings [of a pianoforte] by contact of small pieces of buff leather. |
▪ IV. surd
var. sourd v. Obs., to arise, spring.
| 1509 Hawes Past. Pleas. viii. i. (Percy Soc.) 29 Invencion, Whiche surdeth of the most noble werke Of v. inward wittes. |