axion

American  

[ak-see-on] / ˈæk siˌɒn /

noun

Physics.

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

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axion British  

/ ˈæksɪˌon /

noun

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

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Etymology

Origin of axion

1978; perhaps axi(al current) + -on ¹

Example Sentences

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

“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 lack of a detection, however, would eliminate a large range of potential masses for the axion, and make most current dark matter searches irrelevant.

From Science Daily • Nov. 21, 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

A few have also pursued the axion, a nearly massless particle originally proposed to solve a different problem with the theory of the strong nuclear force.

From Science Magazine • Nov. 20, 2024