crucial, a.
(ˈkruːʃɪəl, -ʃ(ɪ)əl)
[a. F. crucial (Paré 16th c.), f. L. cruc-em cross + -al1.]
1. (Chiefly Anat.) Of the form of a cross, cross-shaped, as crucial incision; spec. the name of two ligaments in the knee-joint, which cross each other in the form of the letter X, and connect the femur and tibia; also applied to ‘the transverse ligament of the atlas and its upper and lower offshoots combined’ (Syd. Soc. Lex.).
| 1706 Phillips (ed. Kersey) s.v. Incision, Crucial Incision, the cutting or lancing of an Impostume or Swelling cross⁓wise. 1767 Gooch Treat. Wounds I. 451 Making an incision quite cross to the bone, from ear to ear; which section is preferable to the crucial, commonly made. 1804 Abernethy Surg. Obs. 256 Between the condyles of the os femoris and the crucial ligaments. 1859 J. Tomes Dental. Surg. 338 In the molar teeth of the lower jaw, the decay sometimes takes a crucial shape. 1861 S. Thomson Wild Fl. iii. (ed. 4) 302 The crucial flowers. |
2. That finally decides between two rival hypotheses, proving the one and disproving the other; more loosely, relating to, or adapted to lead to such decision; decisive, critical. Freq. in trivial use = ‘very important’.
This sense is taken from Bacon's phrase instantia crucis, explained by him as a metaphor from a crux or finger-post at a bivium or bifurcation of a road. Boyle and Newton used the phrase experimentum crucis. These give ‘crucial instance’, ‘crucial experiment’, whence the usage has been extended. Occasionally the sense intended seems to be ‘of the nature of a crux or special difficulty’; see crux.
| [1620 Bacon Nov. Org. ii. xxxvi, Instantias Crucis: translato Vocabulo a Crucibus, quæ erectæ in Biuijs, indicant & signant viarum separationes. Has etiam Instantias Decisorias & Iudiciales, & in Casibus nonnullis Instantias Oraculi, & Mandati appellare consueuimus. 1672 Newton Light & Colours i, The gradual removal of these suspicions at length led me to the Experimentum Crucis.] [Not in Johnson, Todd, or Webster 1828.] 1830 Herschel Stud. Nat. Phil. ii. vi. 150 What Bacon terms ‘crucial instances’, which are phenomena brought forward to decide between two causes, each having the same analogies in its favour. 1869 J. Martineau Ess. II. 134 Crucial experiments for the verification..of his theory. 1874 Helps Soc. Press. xvi. 226 Showing where, at some crucial point of the story, fraud or delusion might enter. 1957 F. King Widow ii. x. 245 That's the crucial time for me, like the first month of a baby. 1963 New Statesman 8 Feb. 195/1 What is crucial, of course, is that these books aren't very good. 1968 Ibid. 23 Feb. 241/2 Twice at crucial moments in this volcanic tragic comedy he asked us to advise him what to do. 1971 Times 19 Jan. 1 (headline) Leaders arrange to meet in private before today's crucial debate. |
¶ 3. Apparently associated with the trying action of a ‘crucible’.
| 1856 Mrs. Browning Aur. Leigh v. 310 And from the imagination's crucial heat Catch up their men and women all a-flame For action. 1860 Lit. Churchman VI. 222/1 This crucial time..which will purge out the dross and tin of popery and dissent. |
Hence ˈcrucially adv., in a crucial manner.
| 1879 H. Grubb in Trans. R. Dubl. Soc. 188 Any one can try this crucially for himself. |