sb. and a. [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. sb. 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. trapezoïde, 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. ? Obs.
A misapplication of the term peculiar to English: now generally given up.
1795. Hutton, Math. Dict., II. 61/1. Trapezoid sometimes denotes a trapezium that has two of its sides parallel to each other. Ibid. (1806), Course Math., I. 297. 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.
1906. Hamilton & Kettle, 2nd Geom. Bk., 39. [Here] trapezoid [is used] for quadrilaterals that have one pair of parallel sides.
† 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. = 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.
