hemihedraladj.

/hɛmɪˈhiːdrəl/

/hɛmɪˈhɛdrəl/

Forms: Also hemiedral.

Etymology: < hemi- prefix 3 + Greek ἕδρα seat, base + -al suffix¹.

Crystallography.

Of a crystal: Having half the number of planes required by the highest degree of symmetry belonging to its system; thus, a tetrahedron is the hemihedral form corresponding to the holohedral octahedron.

ΘΚΠ

the world > matter > chemistry > crystallography (general) > crystal (general) > structures and forms > [adjective] > hemihedral

hemihedral1837

1837 J. D. Dana Syst. Mineral. ii. 19 This species of hemihedral Crystal has been called the inclined hemihedron.

1839–47 Todd's Cycl. Anat. & Physiol. III. 806/1 Triple phosphate..generally occurs in hemihedral six-sided prisms.

1850 C. G. B. Daubeny Introd. Atomic Theory (ed. 2) viii. 264 All the crystals..were alike hemiedral..that is, half of their similar planes or angles were modified independently of the other half.

1878 H. P. Gurney Crystallogr. 39 When the crystal has dissimilar faces at the two ends of the same axis of symmetry, the form to which those faces belong is called hemihedral.

Derivatives

hemiˈhedrally adv.

ΚΠ

1837 J. D. Dana Syst. Mineral. ii. 19 Minerals, whose crystals are hemihedrally modified, are invariably thus modified, if the secondary planes occur, in which the hemihedrism may take place.

This entry has not yet been fully updated (first published 1898; most recently modified version published online June 2022).

单词	hemihedral
释义	hemihedraladj. /hɛmɪˈhiːdrəl//hɛmɪˈhɛdrəl/ Forms: Also hemiedral. Etymology: < hemi- prefix 3 + Greek ἕδρα seat, base + -al suffix¹. Crystallography. Of a crystal: Having half the number of planes required by the highest degree of symmetry belonging to its system; thus, a tetrahedron is the hemihedral form corresponding to the holohedral octahedron. ΘΚΠ the world > matter > chemistry > crystallography (general) > crystal (general) > structures and forms > [adjective] > hemihedral hemihedral1837 1837 J. D. Dana Syst. Mineral. ii. 19 This species of hemihedral Crystal has been called the inclined hemihedron. 1839–47 Todd's Cycl. Anat. & Physiol. III. 806/1 Triple phosphate..generally occurs in hemihedral six-sided prisms. 1850 C. G. B. Daubeny Introd. Atomic Theory (ed. 2) viii. 264 All the crystals..were alike hemiedral..that is, half of their similar planes or angles were modified independently of the other half. 1878 H. P. Gurney Crystallogr. 39 When the crystal has dissimilar faces at the two ends of the same axis of symmetry, the form to which those faces belong is called hemihedral. Derivatives hemiˈhedrally adv. ΚΠ 1837 J. D. Dana Syst. Mineral. ii. 19 Minerals, whose crystals are hemihedrally modified, are invariably thus modified, if the secondary planes occur, in which the hemihedrism may take place. This entry has not yet been fully updated (first published 1898; most recently modified version published online June 2022). < adj.1837
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