What does axion mean?
The axion is a hypothetical elementary particle first proposed in the late 1970s to solve the strong CP problem, a puzzle concerning why the theory of nuclear forces does not exhibit a certain asymmetry that experiments show to be absent or vanishingly small. Postulated by Roberto Peccei and Helen Quinn in 1977 and given its name by Frank Wilczek shortly afterwards, the axion would be extraordinarily light and interact so weakly with ordinary matter that it has never been directly observed. Its appeal extends well beyond this initial puzzle: axions are among the leading candidates for cold dark matter, the invisible substance thought to make up most of the material content of the universe. Dedicated experiments worldwide continue to search for evidence of axions, making the word a fixture of modern physics discourse even though its bearer remains unconfirmed.
nounA hypothetical elementary particle of extremely small mass, postulated in 1977–78 by Roberto Peccei and Helen Quinn and later named by Frank Wilczek, proposed to resolve a problem in quantum chromodynamics known as strong CP violation.
- A hypothetical neutral elementary particle with a very small mass, proposed as a solution to the strong CP problem in quantum chromodynamics and studied extensively as a candidate for cold dark matter.
"Physicists hope that detecting an axion could finally explain why the universe contains far more matter than antimatter."
"Several experiments around the world are now searching for the axion, whose existence would help explain the mysterious nature of dark matter."
"If axions make up the galactic halo, they would drift through our bodies in enormous numbers every second without any detectable interaction."
Standard pluralisation; used when referring to populations or ensembles of the particle.
"Cosmologists model how axions were produced in the early universe."
The axion was literally named after a brand of laundry detergent — physicist Frank Wilczek picked 'Axion' because it sounded like it could 'clean up' an unsolved problem in physics.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of axion
The word axion was coined in the late 1970s by physicist Frank Wilczek, who reportedly chose it because it sounded like 'axis-on' and because it echoed the name of a laundry detergent, fitting his joke that the new particle would 'clean up' the strong CP problem. It was deliberately modelled on the Greek-derived pattern seen in words such as axiom, ultimately evoking the Greek root 'axios', meaning worthy or of value. Since its coinage, the term has remained stable in both British and American scientific usage.
How axion is actually used
Strictly a term of theoretical and experimental particle physics and cosmology; rarely encountered outside scientific literature and popular science writing. Always lowercase, unlike proper nouns of similar form.
Easily confused with axion
An axion is a hypothetical subatomic particle, while an axon is the long fibre of a nerve cell that conducts electrical impulses.
An axiom is a self-evident statement accepted as true without proof, whereas an axion is a conjectured fundamental particle in physics.