a. (sb.) [f. L. type *tangentia (see TANGENCY) + -AL.] Of or pertaining to tangency or a tangent.
1. Of, pertaining to, or of the nature of a tangent; identical with, or drawn at, a tangent to a curve or curved surface.
1630. R. Delamaine, Grammalogia, App. 62. If the Declination be above 38. gr. 3. m. you may move the Tangent of 45. softly alonge by the Tangentiall degrees of Declination in the fixed, untill 45. gr. in the moveable be opposite to 45. gr. in the fixed.
1763. Phil. Trans., LIII. 68. The proposed demonstration of this tangential property.
1828. J. M. Spearman, Brit. Gunner, 265. The apparent level is a straight line tangential to the surface of the earth, or true level.
1881. Tait, in Nature, XXV. 128. The glass is extended in a radial and compressed in a tangential direction.
b. Of motion or force: Acting along a tangent to a curved line or surface.
1709. Steele, Tatler, No. 43, ¶ 7. The Tangential and Centripetal Forces, by their Counter-struggle, make the Celestial Bodies describe an exact Ellipsis.
1768. Tucker, Lt. Nat. (1834), I. 413. He might give the heavy planets their tangential motion by one strong and exactly poised stroke.
1880. Bessey, Botany, 129. The tangential growth of the surrounding cells.
1883. Science, I. 523/1. The tangential tension of the bark increases with the growth of the stem.
c. Of a thing: That lies in a tangent to a curved surface.
1854. J. Scoffern, in Orr’s Circ. Sc., Chem., 388. One part [of a globular box] is furnished with a tangential jet.
1899. Allbutt’s Syst. Med., VIII. 331. The tangential fibres of the cortex.
1901. A. J. Evans, in Oxf. Univ. Gaz., 12 Feb., 339/2. A small vase with incised returning spirals and tangential leaves.
1905. Bond, Goth. Archit., 164. The ambulatory with tangential chapels.
d. spec. (a) of the spokes of a wheel (as in a bicycle): Arranged as tangents to the hub. (b) Of a fabric (as a tire-cover): Having layers of thread lying diagonally from edge to edge, so as to distribute the strain.
1898. Cycling, 63. The best results are obtained from a fabric which … consists of layers of independent threads running diagonally from edge to edge of the cover and not interwoven. This is called a ‘tangential’ fabric because the pull travels lengthwise along the threads (as in a tangent spoke) and not across them.
2. fig. Going off suddenly ‘at a tangent’; erratic; divergent; digressive.
1867. F. H. Ludlow, Genre Pict., Little Briggs & I, 199. A remedy to this day sovereign … for all tangential aberrations from the back of a colt or the laws of society.
1876. T. Hardy, Ethelberta (1890), 297. Those devious impulses and tangential flights which spoil the works of every would-be schemer who instead of being wholly machine is half heart.
1903. Spectator, 31 Jan., 184/2. A collection of mixed and tangential information.
1907. Halsham, Lonewood Corner, xvii. 185. With a good deal of hauling the argument back into the right line from several sorts of tangential wandering.
b. That merely touches a subject or matter.
1825. Hazlitt, Spirit of Age, Coleridge (1886), 46. Our author’s mind is (as he himself might express it) tangential. There is no subject on which he has not touched, none on which he has rested.
1885. O. W. Holmes, Emerson, 165. Emerson had only tangential relations with the experiment.
B. sb. Geom. Tangential of a point (in a curve of the third or higher order), the point at which a tangent at the given point meets the curve again.
1858. Cayley, Coll. Math. Papers, II. 558. A derivative which may be termed the ‘tangential’ of a cubic, viz. the tangent at the point (x, y, z) of the cubic curve (*)(x, y, z)2 = 0 meets the curve in a point (ξ, η, ζ), which is the tangential of the first-mentioned point. 1859 Ibid., IV, 183.
1879. G. Salmon, Higher Plane Curves, v. (ed. 3), 130.
Hence Tangentiality, the quality or condition of being tangential.
1862. Mechanics’ Mag., VII. (N.S.), 18 April, 269/2. In such instance tangentiality had been secured, and not parallelism maintained.
1889. Philos. Mag., April, 335. The perpendicularity of E and the tangentiality of H to the surface.
