heptagonaladj.n.
/hɛpˈtaɡənəl/ a. Having seven angles and seven sides. heptagonal numbers, the series of polygonal adj. and n. numbers 1, 7, 18, 34, 55, 81, etc. formed by continuous summation of the arithmetical series 1, 6, 11, 16, 21, 26, etc.
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the world > space > shape > angularity > specific angular shape > [adjective] > polygonal > heptagonal
heptagonal1612
septilateral1650
septangular1656
septangled1702
heptangular1706
septagon1756
the world > relative properties > number > geometry > shape or figure > [adjective] > two-dimensional > heptagonal
heptagonal1612
septilateral1650
septangular1656
heptahedrical1658
septangled1702
heptangular1706
septagon1756
heptahedral1758
1612 J. Selden in M. Drayton Poly-olbion xi. Illustr. 184 In a Circle describe an Heptagonall and Equilaterall figure; from whose euery side shall fall equilaterall Triangles.
1690 W. Leybourn Cursus mathematicus 279 It is called a Heptagonal Pyramide.
1796 C. Hutton Math. & Philos. Dict. (at cited word) One property..of these Heptagonal numbers is, that if any one of them be multiplied by 40, and to the product add 9, the sum will be a square number.
1828 J. Stark Elements Nat. Hist. I. 398 Body heptagonal, yellowish brown, variegated with narrow transverse deep brown bars.
1853 J. Ruskin Stones of Venice II. iii. 37 We have therefore, externally a heptagonal apse.
b. n. A heptagonal number.
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1796 C. Hutton Math. & Philos. Dict. (at cited word) The Heptagonals are formed by adding continually the terms of the arithmeticals.
This entry has not yet been fully updated (first published 1898; most recently modified version published online March 2018).
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adj.n.1612