different between isosceles vs disphenoid

English

Etymology

Borrowed from Latin ?soscel?s, from Ancient Greek ????????? (isoskel?s, “equal-legged”), from ???? (ísos, “equal”) +? ?????? (skélos, “leg”) +? -?? (-?s, adjective suffix).

Pronunciation

• IPA^(key): /a??s?s?li?z/

Adjective

isosceles (not comparable)

1. (geometry) Having (at least) two sides of equal length, used especially of a triangle or trapezoid.

Usage notes

• A triangle with three equal sides is normally described as equilateral, even though it can be regarded as a special case of isosceles triangle.

Translations

Further reading

• Isosceles triangle on Wikipedia.Wikipedia
• Isosceles (disambiguation) on Wikipedia.Wikipedia

Anagrams

• solecises

Latin

Etymology

Borrowed from Ancient Greek ????????? (isoskel?s), from ???? (ísos, “equal”) +? ?????? (skélos, “leg”) +? -?? (-?s, adjective suffix).

Pronunciation

• (?soscel?s): (Classical) IPA^(key): /i??sos.ke.le?s/, [i??s??s?k???e?s?]
• (Ecclesiastical) IPA^(key): /i?so.?e.les/, [i?s?????l?s]
• (?sosceles): (Classical) IPA^(key): /i??sos.ke.les/, [i??s??s?k????s?]
• (Ecclesiastical) IPA^(key): /i?so.?e.les/, [i?s?????l?s]

Adjective

?soscel?s (genitive ?soscelis); third-declension one-termination adjective

1. (geometry) isosceles (having equal legs)

Declension

Third-declension one-termination adjective (Greek-type).

¹It is unknown if Classical Latin preserved (or would have preserved) the shortness of the original Greek short ending.Notes:

• The Greek masculine and feminine nominative singular is ????????? (isoskel?s), while the masculine and feminine vocative singular and the neuter nominative, accusative and vocative singular are ????????? (isoskelés). Maybe Latin preserved the short length of the epsilon (?), or maybe it did not so that the declension became similar to Latin third declension adjectives of one ending (like felix).
• This word is often used together with triangulum n and rarer with triangulus m.

References

• ?sosc?les in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
• ?sosc?l?s in Gaffiot, Félix (1934) Dictionnaire illustré Latin-Français, Hachette, page 860/3

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