# duality

[doo-al-i-tee, dyoo-]

- a dual state or quality.
- Mathematics. a symmetry within a mathematical system such that a theorem remains valid if certain objects, relations, or operations are interchanged, as the interchange of points and lines in a plane in projective geometry.

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## Origin of duality^{}

Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

## Examples from the Web for duality

### Contemporary Examples

#### Buried halfway underground, the work has a duality of life and death—is it growing or is it a tomb?

#### “We liked the duality of these low-plunging costumes because Amy could slip from being confident to vulnerable,” says Wilkinson.

Creating American Hustle’s Sexy, Oscar-Nominated Look: From Pasties to The PlazaMarlow Stern

February 23, 2014

#### Much like the duality of his shop, Simon is half goateed-rocker, half cicerone sage.

#### That duality is represented by Tom Ford more than any other designer.

#### As a ballerina, to embody the duality of the Swan Queen and the black swan can be a fiendishly difficult task.

### Historical Examples

#### The weakness of the play, as I have said, lies in its duality of action.

John LylyJohn Dover Wilson

#### Duality is the root, out of which alone, for mortals, happiness can spring.

The Substance of a DreamF. W. Bain

#### This then is the duality of my day and my night being: a duality so bitter to an adolescent.

Fantasia of the UnconsciousD. H. Lawrence

#### In her, the duality of her being had created two distinct lives.

Casa Braccio, Volumes 1 and 2 (of 2)F. Marion Crawford

#### In a way, every one must have a sort of duality—a good and evil principle.

Casa Braccio, Volumes 1 and 2 (of 2)F. Marion Crawford

## duality

- the state or quality of being two or in two parts; dichotomy
- physics the principle that a wave-particle duality exists in microphysics in which wave theory and corpuscular theory are complementary. The propagation of electromagnetic radiation is analysed using wave theory but its interaction with matter is described in terms of photons. The condition of particles such as electrons, neutrons, and atoms is described in terms of de Broglie waves
- geometry the interchangeability of the roles of the point and the plane in statements and theorems in projective geometry

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Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

## Word Origin and History for duality

### n.

late 14c., from Old French dualité (14c.), from Late Latin dualitas, from Latin dualis (see dual).

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Online Etymology Dictionary, © 2010 Douglas Harper