ditrigonaladj.
/dʌɪˈtrɪɡənəl/ Crystallography.
Having six (dihedral) angles, of which the first, third, and fifth are equal, and also the second, fourth, and sixth, but those of the one set not equal to those of the other. (Cf. dihexagonal adj., ditetragonal adj.)
ΚΠ
1878 H. P. Gurney Crystallogr. 60 Some minerals..appear to possess a truly hexagonal and not merely a trigonal or ditrigonal symmetry.
1895 N. Story-Maskelyne Crystallogr. v. §116. 133 A form with six poles grouped round the axis, that may be viewed as an axis of ditrigonal symmetry.
1895 N. Story-Maskelyne Crystallogr. vii. §244. 293 The ditrigonal scalenohedron.
Derivatives
diˈtrigonally adv.
ΚΠ
1895 N. Story-Maskelyne Crystallogr. vii. §246. 296 The summit-quoins are symmetrical ditrigonally on the axis.
This entry has not yet been fully updated (first published 1897; most recently modified version published online June 2018).
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adj.1878