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.

Despite working with limited resources, they were able to establish new experimental limits on axion properties, demonstrating that smaller experiments can still advance one of physics' biggest unresolved problems.

From Science Daily • Apr. 27, 2026

The high-speed motion of orbiting sensors increases the coupling between axion halos and nucleon spins, producing a tenfold sensitivity improvement compared with Earth-based dark matter searches.

From Science Daily • Dec. 6, 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

"It would be a real shame if a supernova went off tomorrow and we missed an opportunity to detect the axion -- it might not come back for another 50 years."

From Science Daily • Nov. 21, 2024

"This has really led us to thinking about neutron stars as optimal targets for searching for axions as axion laboratories," Safdi said.

From Science Daily • Nov. 21, 2024

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