duality

American  

[doo-al-i-tee, dyoo-] / duˈæl ɪ ti, dju- /

noun

dualities plural

1. a dual state or quality.

2. 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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duality British  

/ djuːˈælɪtɪ /

noun

1. the state or quality of being two or in two parts; dichotomy

2. 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

3. geometry the interchangeability of the roles of the point and the plane in statements and theorems in projective geometry

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Other Word Forms

Derived Forms

• nonduality
  noun

Inflected Forms

Nouns

• dualities
  plural

Etymology

Origin of duality

1350–1400; Middle English dualitie < Late Latin duālitās. See dual, -ity

Explanation

As hinted at by the word "dual" within it, duality refers to having two parts, often with opposite meanings, like the duality of good and evil. If there are two sides to a coin, metaphorically speaking, there's a duality. Peace and war, love and hate, up and down, and black and white are dualities. Another term for a duality is a dichotomy. Duality has technical meanings in geometry and physics. In geometry, duality refers to how points and planes have interchangeable roles in projective geometry. In physics, duality is the property of matter and electromagnetic radiation to be understood best through wave theory or particle theory.

Example Sentences

See Examples For:

duality dualities

Much like the twins, their abilities appear predicated on a complementary duality to assist their masters.

From Salon ● Jul. 18, 2026

Mabille's collection for haute couture week was all about getting more than you bargained for with its theme of duality.

From BBC ● Jul. 9, 2026

Among the most important discoveries was wave-particle duality, the idea that particles can also act like waves.

From Science Daily ● Apr. 28, 2026

This is typical Morris: a claim of duality that demands the spotlight while refusing to be knowable.

From The Wall Street Journal ● Apr. 23, 2026

One was the so- called wave-particle duality of nature at the infinitesimal scale: experiments sometimes showed light and electrons behaving like particles, and other times as waves.

From "Big Science" by Michael Hiltzik

In “The Bear’s” White, Cooper saw an actor who’d capture Springsteen’s dualities — swagger and fragility, quiet intensity and vulnerability — and who was committed to total immersion.

From Los Angeles Times ● Oct. 28, 2025

That speech America Ferrera gives in “Barbie” really highlights these impossible dualities that women have to embrace.

From Seattle Times ● Mar. 8, 2024

It’s these dualities of Yendry that connect with a growing fan base all over the world.

From Los Angeles Times ● Dec. 7, 2023

Exulting in his victory Tuesday night, Senator Raphael Warnock showcased the dualities that have defined his career in public life.

From New York Times ● Dec. 7, 2022

Then, from about 1994, people started discovering what are called dualities: different string theories and different ways of curling up the extra dimensions could lead to the same results in four dimensions.

From "A Brief History of Time: And Other Essays" by Stephen Hawking

Related Words

• artifice
• chicanery
• deceit
• dishonesty
• falsehood
• hypocrisy