| 释义 |
irrational, a. and n.|ɪˈræʃənəl|
[ad. L. irratiōnāl-is, f. ir- (ir-2) + ratiōnāl-is rational.]
A. adj.
1. Not endowed with reason.
c1470Henryson Mor. Fab. iii. (Cock & Fox) i, Thocht brutall beistis be irrationall, That is to say, wantand discretioun. 1635J. Hayward tr. Biondi's Banish'd Virg. 128 Confirmed in such an opinion by the nature of irrationall animals. 1661Lovell Hist. Anim. & Min. Introd., As for Animals, they are animate bodies, and sentient, having locall motion, and are either irrationall or rationall. 1752Hume Ess. & Treat. (1777) I. 221 Nothing has a greater effect on all plants and irrational animals. 1826Scott Woodst. iv, That may be true of the more irrational kinds of animals among each other.
2. Contrary to or not in accordance with reason; unreasonable, utterly illogical, absurd.
1641F. Greville Eng. Episc. 23 All my acts may be Irrationall, and yet not sinfull. 1664–94South Twelve Serm. II. 15 This certainly is a Confidence of all others the most ungrounded and irrational. 1796Burke Regic. Peace i. Wks. VIII. 84 Inconsiderate courage has given way to irrational fear. 1825McCulloch Pol. Econ. ii. ii. 123 Nothing can be more irrational and absurd, than that dread of the progress of others in wealth and civilization that was once so prevalent. 1875Jowett Plato (ed. 2) V. 186 If men cannot have a rational belief, they will have an irrational.
3. Math. Of a number, quantity, or magnitude: Not rational; not commensurable with ordinary quantities such as the natural numbers; not expressible by an ordinary (finite) fraction, proper or improper (but only by an infinite continued fraction, or an infinite series, e.g. an interminate decimal). Usually applied to roots (denoted by the radical sign √, or in Alg. by fractional indices) whose value cannot be exactly found in finite terms of the unit, or to expressions involving such roots; the same as surd.
In translations of Euclid (following his peculiar use of ἄλογος), applied to a quantity which is itself incommensurable with the unit and whose square is incommensurable with that of the unit.
1551Recorde Pathw. Knowl. ii. Pref., Numbres and quantitees surde or irrationall. 1673Wallis in Rigaud Corr. Sci. Men (1841) II. 567, I depress the irrational part √3200 by dividing 3200 by the greatest square number I can. 1743Emerson Fluxions 45 The Fluent of an irrational Fluxion may sometimes..be found by assuming an indetermin'd Series. 1827Hutton Course Math. I. 82 The cube root of 8 is rational, being equal to 2; but the cube root of 9 is surd or irrational. 1879Thomson & Tait Nat. Phil. I. i. §359 We may have..three different values of one algebraic irrational expression.
4. Gr. Pros. Said of a syllable having a metrical value not corresponding to its actual time-value, or of a metrical foot containing such a syllable.
1844Beck & Felton tr. Munk's Metres 17 There is also an irrational (ἄλογον) relation which cannot be measured by the unit. 1883Jebb Œdipus Tyrannus p. lxxiii, The anacrusis..is an irrational syllable, a long serving for a short.
B. n.
1. A being not endowed with reason; one not guided by reason.
1646J. Hall Horæ Vac. 16 We live under the Colours of vertue; in other actions we are no more than Irrationals. 1713Derham Phys.-Theol. iv. xiii. (1714) 236 The architectonick Faculty of Animals, especially the Irrationals. 1810D. Savile Disc. Revel. 280 Infants and irrationals neither have nor can have clear, distinct, and explicit knowledge of Christ. 1858Gen. P. Thompson Audi Alt. I. lxi. 239 There is that in progress, which will put down the reign of irrationals whether on four feet or on two.
2. Math. An irrational number or quantity; a surd. (In quot. 1875 applied to a number having no measure but unity, a prime number: cf. incommensurable 1 b.)
1674S. Jeake Arith. (1696) 360 In pursuit of Species, I now come to Irrationals, which in their Operations..follow Surds. 1875Jowett Plato (ed. 2) III. 115 Two incommensurable diameters, i.e. the two first irrationals, 2 and 3. |