axion

American

[ak-see-on] / ˈæk siˌɒn /

noun

Physics.

a hypothetical particle having no charge, zero spin, and small mass: postulated in some forms of quantum chromodynamics.

axion British

/ ˈæksɪˌon /

noun

physics a hypothetical neutral elementary particle postulated to account for certain conservation laws in the strong interaction

"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

Etymology

Origin of axion

1978; perhaps axi(al current) + -on ¹

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

axion

In solving this puzzle, the PQ symmetry introduces the axion, a hypothetical particle that is a leading candidate for dark matter.

From Science Daily ● Dec. 7, 2025

In this model, the PQ symmetry is kept as a global symmetry rather than being "gauged," which protects the delicate axion physics needed to solve the strong-CP problem.

From Science Daily ● Dec. 7, 2025

“If dark matter were a QCD axion, it would essentially be invisible to us,” O’Hare told Salon in a video call.

From Salon ● Dec. 26, 2024

The current best candidate for dark matter is the axion, a particle that fits nicely within the standard model of physics and solves several other outstanding puzzles in particle physics.

From Science Daily ● Nov. 21, 2024

The axion is distinctly different from another lightweight, weakly-interacting particle, the neutrino, which only interacts through gravity and the weak force and totally ignores the electromagnetic force.

From Science Daily ● Nov. 21, 2024

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Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023