# trigonal

[trig-uh-nl] /ˈtrɪg ə nl/
1.
of, relating to, or shaped like a triangle; having three angles; triangular.
2.
Crystallography. having threefold symmetry.
Origin of trigonal
1560-1570
1560-70; trigon + -al1
Related forms
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the Web for trigonal
Historical Examples
• Parietes ribbed, mottled purplish-red; orifice broad, trigonal, hardly toothed.

Charles Darwin
• The leaves are trigonal; they are very short, and they are laid over each other like scales in four rows.

Jane Loudon
• When the whorls are angulated, a trigonal aperture is the result, as in many species of Trochus.

George Brettingham Sowerby
• Fig. 73 represents a crystal of tourmaline with the trigonal prism , hexagonal prism , and a trigonal pyramid at each end.

• Mactracea (plates, fig. 77 to 88), the cartilage placed in a trigonal pit, with a small external ligament.

George Brettingham Sowerby
• All other forms, in which the faces are neither parallel nor perpendicular to the triad axis, are trigonal pyramids.

• All the prisms are trigonal prisms; and perpendicular to these are two pedions.

• The horns are trigonal, laterally compressed and knotted on the upper edge.

Robert A. Sterndale
• trigonal trapezohedron (fig. 74), bounded by six trapezoidal faces.

• The cartilage placed in a trigonal pit with a small external ligament.

George Brettingham Sowerby
British Dictionary definitions for trigonal

## trigonal

/ˈtrɪɡənəl/
1.
another word for triangular (sense 1)
2.
Also rhombohedral. relating or belonging to the crystal system characterized by three equal axes that are equally inclined and not perpendicular to each other
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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trigonal in Science
 trigonal   (trī-gō'nəl)    Relating to a crystal having three axes of equal length intersecting at oblique angles. This crystal system is considered a subset of the hexagonal system. The mineral quartz has trigonal crystals. Also called rhombohedral. See illustration at crystal.
The American Heritage® Science Dictionary