from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The quality or character of being twofold; dichotomy.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A classification into two subclasses or opposed parts.
- n. The interchangeability of points and planes.
- n. The mathematical equivalence of two seemingly different theoretical descriptions of a physical system.
from the GNU version of the Collaborative International Dictionary of English
- n. The quality or condition of being two or twofold; dual character or usage.
from The Century Dictionary and Cyclopedia
- n. The state of being two, or of being divided into two; twofold division or character; twoness.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. (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
- n. being twofold; a classification into two opposed parts or subclasses
- n. (geometry) the interchangeability of the roles of points and planes in the theorems of projective geometry
From Latin duālitās. (Wiktionary)