plagihedraladj.

Brit.

/ˌpleɪdʒɪˈhiːdr(ə)l/, U.S.

/ˌpleɪdʒəˈhidr(ə)l/

Forms: 1800s plagiedral, 1800s– plagihedral.

Origin: A borrowing from Greek, combined with an English element; modelled on a French lexical item. Etymons: Greek πλάγιος , -hedral comb. form.

Etymology: < ancient Greek πλάγιος oblique, slanting (see plagio- comb. form) + -hedral comb. form, after French plagièdre (R. J. Haüy 1797, in Jrnl. des mines 28 255). N.E.D.(1907) also gives (-he·drăl) /-ˈhɛdrəl/ as the pronunciation of the second element.

Crystallography. Now rare.

Having or designating certain symmetrical crystal faces whose axes are each at the same oblique angle to the vertical, occurring esp. in quartz, where the orientation of these faces indicates whether the crystal is laevorotatory or dextrorotatory (figurative in quot. 1999).

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plagihedral1816

1816 R. Jameson Treat. External Characters Minerals (ed. 2) 207 [A crystal is said to be] Plagihedral.., when it has facets which are situated obliquely.

1854 B. Powell Pereira's Lect. Polarized Light (ed. 2) 257 In that form of quartz termed by Haüy plagiedral.., it has been found that when the unsymmetrical or plagiedral faces lean to the right, the polarization is right-handed, and, vice versâ.

1895 N. Story-Maskelyne Crystallogr. 316 A crystal of quartz..will, if right-handed, present on three alternate quoins at each end of the prism plagihedral faces arranged in the form of a right-handed screw.

1976 Trans. Amer. Philos. Soc. 66 63/1 On certain non-symmetrical prismatic varieties of quartz which Haüy had labeled ‘plagihedral’ and which possessed optical rotatory power, there were secondary faces which, as Herschel put it, ‘lean or tend, as it were’ to the left or to the right of the principal axis.

1999 R. R. Wilson Boundaries 95 When she has grown older, her face will rupture into plagihedral surfaces, the distinct planes thickening and angling away from each other.

This entry has been updated (OED Third Edition, June 2006; most recently modified version published online March 2022).

单词	plagihedral
释义	plagihedraladj. Brit. /ˌpleɪdʒɪˈhiːdr(ə)l/, U.S. /ˌpleɪdʒəˈhidr(ə)l/ Forms: 1800s plagiedral, 1800s– plagihedral. Origin: A borrowing from Greek, combined with an English element; modelled on a French lexical item. Etymons: Greek πλάγιος , -hedral comb. form. Etymology: < ancient Greek πλάγιος oblique, slanting (see plagio- comb. form) + -hedral comb. form, after French plagièdre (R. J. Haüy 1797, in Jrnl. des mines 28 255). N.E.D.(1907) also gives (-he·drăl) /-ˈhɛdrəl/ as the pronunciation of the second element. Crystallography. Now rare. Having or designating certain symmetrical crystal faces whose axes are each at the same oblique angle to the vertical, occurring esp. in quartz, where the orientation of these faces indicates whether the crystal is laevorotatory or dextrorotatory (figurative in quot. 1999). ΘΚΠ the world > matter > chemistry > crystallography (general) > crystal (general) > crystals (other miscellaneous) > [adjective] > crystal faces > plagihedral plagihedral1816 1816 R. Jameson Treat. External Characters Minerals (ed. 2) 207 [A crystal is said to be] Plagihedral.., when it has facets which are situated obliquely. 1854 B. Powell Pereira's Lect. Polarized Light (ed. 2) 257 In that form of quartz termed by Haüy plagiedral.., it has been found that when the unsymmetrical or plagiedral faces lean to the right, the polarization is right-handed, and, vice versâ. 1895 N. Story-Maskelyne Crystallogr. 316 A crystal of quartz..will, if right-handed, present on three alternate quoins at each end of the prism plagihedral faces arranged in the form of a right-handed screw. 1976 Trans. Amer. Philos. Soc. 66 63/1 On certain non-symmetrical prismatic varieties of quartz which Haüy had labeled ‘plagihedral’ and which possessed optical rotatory power, there were secondary faces which, as Herschel put it, ‘lean or tend, as it were’ to the left or to the right of the principal axis. 1999 R. R. Wilson Boundaries 95 When she has grown older, her face will rupture into plagihedral surfaces, the distinct planes thickening and angling away from each other. This entry has been updated (OED Third Edition, June 2006; most recently modified version published online March 2022). < adj.1816
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