trapezoid, n. and a.
(ˈtræpɪzɔɪd, trəˈpiːzɔɪd)
[ad. mod.L. trapezoïdēs, a. late Gr. τραπεζοειδής, neut. -ές table-like (Proclus 450), f. τράπεζα table: see -oid. Cf. F. trapézoïde (1652 in Hatz.-Darm.).]
A. n.
1. Geom. a. A quadrilateral figure no two of whose sides are parallel. (Often called by English writers (in 19th c.) trapezium.)
This is the sense for which Proclus introduced the term τραπεζοειδές; it is retained in F. trapézoïde, Ger. trapezoïd, etc. See etymol. note to trapezium.
| 1706 Phillips (ed. Kersey), Trapezoid, a Geometrical Figure that has all its four Sides and Angles unequal, and no Sides parallel. 1753 Chambers Cycl. Supp., Trapezoid, in geometry, a plane irregular figure, having four sides, no two of which are parallel to each other. 1788 T. Taylor Proclus' Comm. I. 176 Of non-parallelograms, some have only two parallel sides,..others have none of their sides parallel. And those are called Trapeziums, but these Trapezoids. 1851 R. F. Burton Goa 274 Its shape is a trapezoid, for though quadrilateral, none of its sides are equal or even. |
b. With some: A quadrilateral figure having only two sides parallel: = trapezium 1 b. Now U.S.
A misapplication of the term orig. peculiar to English.
| 1795 Hutton Math. Dict. II. 611/1 Trapezoid sometimes denotes a trapezium that has two of its sides parallel to each other. 1806 ― Course Math. I. 291 A Trapezoid, or Trapezium having two Sides Parallel. 1846 Potts Euclid 45 Sometimes an irregular four-sided figure which has two of its sides parallel, is called a trapezoid. 1879 in Cassell's Techn. Educ. ii. 124 If any two of the sides are parallel to each other the figure is called a trapezoid. 1901 [see trapezium 1 c]. 1906 Hamilton & Kettle 2nd Geom. Bk. 39 [Here] trapezoid [is used] for quadrilaterals that have one pair of parallel sides. 1925 F. E. Seymour Plane Geom. ii. 103 If the non-parallel sides of a trapezoid are equal, the trapezoid is called an isosceles trapezoid. 1972 Whitaker's Almanack 1973 902/2 Flag [of Kuwait].—Three horizontal stripes of green, white and red, with black trapezoid next to staff. 1975 Sci. Amer. Jan. 110/3 The matrix is stretched to a trapezoid, then the artist copies the picture by filling in the trapezoidal cells. 1977 Monitor (McAllen, Texas) 6 Jan. e–2/4 The Incas apparently adopted many things from the Mollos, of which the trapezoid is only one. |
† c. Formerly applied to an irregularly quadrate solid with neither pair of sides parallel. Obs.
(Here -oid appears to have the same sense as in ellipsoid, paraboloid.)
| 1704 J. Harris Lex. Techn., Trapezoid is a solid irregular Figure, having four Sides not parallel to one another. [The only sense given.] 1795 in Hutton Math. Dict. II. 611/1 [as second sense]. |
2. Anat. A bone of the wrist, the second of the distal row of the carpus: so called from its shape. (Also in L.-Gr. form trapezoides; Fr. trapézoïde.)
| 1831 R. Knox Cloquet's Anat. 135 The Trapezoides (os multangulum minus), is smaller than the trapezium. 1840 E. Wilson Anat. Vade M. (1842) 113 When seen from before, it has a quadrilateral form: it is named trapezoid. 1855 Holden Hum. Osteol. (1878) 161 The trapezium and trapezoid form a shallow socket for part of the scaphoid. |
B. adj. a. = trapezoidal. (In all the quots. improperly used for trapezial.)
| 1819 G. Samouelle Entomol. Compend. 195 Thorax trapezoid, broad behind. 1826 Kirby & Sp. Entomol. IV. 264 Trapezoid... Quadrilateral, with two sides unequal and parallel. Note. We have departed from the more usual definition of trapezoid, ‘An irregular figure whose four sides are not parallel’, because the above is best suited to forms in insects. 1840 E. Wilson Anat. Vade M. (1842) 124 The internal lateral ligament is a broad and trapezoid layer of ligamentous fibres. |
b. Anat. trapezoid body: = trapezium 2 b. trapezoid bone: = A. 2. trapezoid ligament (F. ligament trapézoïde), the coraco-clavicular ligament. trapezoid line: see quot. 1890.
| 1890 Billings Nat. Med. Dict. s.v., T[rapezoid] bone, second bone of distal row of wrist... T. line, a rough ridge for attachment of trapezoid ligament on under surface of clavicle. 1899 Allbutt's Syst. Med. VI. 804 Degeneration of the trapezoid body. |