from The American Heritage® Dictionary of the English Language, 4th Edition

  • adj. Mathematics Formed by or having two plane faces; two-sided.
  • adj. Mathematics Relating to, having, or forming a dihedral angle.
  • n. Mathematics A dihedral angle.
  • n. Mathematics A dihedral group.
  • n. Aeronautics The upward or downward inclination of an aircraft wing from true horizontal.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. An angle between two plane surfaces
  • n. The upward slope of an aircraft's wing
  • n. The angle between pairs of chemical bonds separated by a third bond
  • adj. Consisting of, relating to or contained between two plane surfaces.

from the GNU version of the Collaborative International Dictionary of English

  • adj. Having two plane faces.
  • adj. Of a kite or an aëroplane, having wings that make with one another a dihedral angle, esp. when the angle between the upper sides is less than 180°.
  • adj. Of wing pairs, inclined at an upward angle to each other.

from The Century Dictionary and Cyclopedia

  • Having two sides, as a figure; having two plane faces, as a crystal.
  • n. In geometry, a pair of consecutive faces of an angloid.


Sorry, no etymologies found.



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  • From my climbing days, a near-vertical stretch of a route to be scaled via the inner angle of 2 intersecting faces of rock and/or ice. Sometimes dihedrals were a simple execution to mount and surpass, with the hands and "protection" (inserted and firmly-lodged hardware such as reversible cams, nuts, pitons, etc., to which carabiners and slings holding the rope were attached) utilizing a crack at the intersection of the faces while the feet took advantage of and found purchase upon irregularities on the opposing faces.

    January 15, 2009