different between crystal vs disphenoid

English

Alternative forms

• crystall (obsolete)
• chrystal (obsolete)

Etymology

From Middle English crystal, cristal, cri?stall, from Old English cristalla (“crystal”), a borrowing from Latin crystallum (“crystal, ice”) (later reinforced from Anglo-Norman cristall and Middle French cristal, from Latin crystallum), from Ancient Greek ?????????? (krústallos, “clear ice”), from ????? (krúos, “frost”), from the Proto-Indo-European *krus-, *kru- (“hard, hard outer surface, crust”).

Pronunciation

• enPR: kr?s?t?l, IPA^(key): /?k??st?l/

Noun

crystal (countable and uncountable, plural crystals)

1. (countable) A solid composed of an array of atoms or molecules possessing long-range order and arranged in a pattern which is periodic in three dimensions.

   Synonym: grain

   Antonyms: amorphous, glass

2. (countable) A piece of glimmering, shining mineral resembling ice or glass.
3. (uncountable) A fine type of glassware, or the material used to make it.
4. (uncountable, slang) Crystal meth: methamphetamine hydrochloride.
5. The glass over the dial of a watch case.

Derived terms

Descendants

• ? Japanese: ????? (kurisutaru)

Translations

Adjective

crystal (not comparable)

1. Very clear.

   "Do I make myself clear?" / "Crystal."

References

• Douglas Harper (2001–2021) , “crystal”, in Online Etymology Dictionary

English

Etymology

From di- (“twice, double”) +? sphenoid (“wedge-shaped crystal or bone of the skull”).

Adjective

disphenoid (not comparable)

1. (mineralogy) Of or pertaining to a wedge-shaped crystal form of the tetragonal or orthorhombic system.
2. (mineralogy) Of or pertaining to a crystal form bounded by eight scalene triangles arranged in pairs, constituting a tetragonal scalenohedron.

Noun

disphenoid (plural disphenoids)

1. (geometry) A non-regular tetrahedron whose four faces are congruent acute-angled triangles.
   • 1973, H. S. M. Coxeter, 3rd Edition, unnumbered page,

     To make a model of a disphenoid, cut out an acute angled triangle and fold it along the joins of the mid-points of the sides. The disphenoid is said to be rhombic or tetragonal according as the triangle is isosceles or scalene.

   • 1977, Elizabeth A. Wood, Crystals and Light: An Introduction to Optical Crystallography, 2nd Revised Edition, page 8,

     If you rotate the [tetragonal] disphenoid 90° around its 2-fold axis and then perform the operation of inversion through the center-point of the object, it will occupy its original position again.

   • 1993, Horst Martini, A Hierarchical Classification of Euclidean Polytopes with Regularity Properties, Tibor Bisztriczky, Peter McMullen, Rolf Schneider, Asia Ivic Weiss (editors), Polytopes: Abstract, Convex and Computational, Proceedings of the NATO Advanced Study Institute, page 83,

     In addition it should be remarked that there are two types of disphenoids, with different symmetries: the tetragonal disphenoid (having isosceles facets) and the rhombic one.

Synonyms

• (non-regular tetrahedron with congruent faces): bisphenoid, equifacial tetrahedron, isosceles tetrahedron

Derived terms

• rhombic disphenoid
• snub disphenoid
• tetragonal disphenoid