from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun The quality or character of being twofold; dichotomy.

from The Century Dictionary.

  • noun The state of being two, or of being divided into two; twofold division or character; twoness.

from the GNU version of the Collaborative International Dictionary of English.

  • noun The quality or condition of being two or twofold; dual character or usage.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun A classification into two subclasses or opposed parts.
  • noun projective geometry The interchangeability of points and planes.
  • noun mathematics, physics The mathematical equivalence of two seemingly different theoretical descriptions of a physical system.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun (physics) the property of matter and electromagnetic radiation that is characterized by the fact that some properties can be explained best by wave theory and others by particle theory
  • noun being twofold; a classification into two opposed parts or subclasses
  • noun (geometry) the interchangeability of the roles of points and planes in the theorems of projective geometry


from Wiktionary, Creative Commons Attribution/Share-Alike License

From Latin duālitās.


Help support Wordnik (and make this page ad-free) by adopting the word duality.



Log in or sign up to get involved in the conversation. It's quick and easy.