axion

noun

ax·​ion ˈak-sē-(ˌ)än 

: a hypothetical subatomic particle of low mass and energy that is postulated to exist because of certain properties of the strong force

Examples of axion in a Sentence

Recent Examples on the Web

But as time goes on, the axions will dilute and lose steam, allowing for the negative cosmological constant to take over, the authors propose. —Paul Sutter, Space.com, 24 July 2025

For decades, researchers focused on two candidate particle types: weakly interacting massive particles (WIMPs) and axions. —Lyndie Chiou, Quanta Magazine, 7 May 2024

That includes perhaps the leading dark matter candidate at the moment, axions. —Robert Lea, Space.com, 7 July 2025

For example, extremely light particles, such as axions or special types of photons considered candidates for dark matter, could absorb the rotational energy of black holes, amplifying their signals. —Manon Bischoff, Scientific American, 12 May 2025

Word History

Etymology

axi(al) + -on entry 2

Note: The name axion was introduced by the American physicist Stephen Weinberg (born 1933) in "A New Light Boson?", Physical Review Letters, vol. 40, no. 4 (January 23, 1978), p. 233; and by American physicist Frank Wilczek (born 1951) in "Problems of Strong P and T Invariance in the Presence of Instantons," Physical Review Letters, vol. 40, no. 5, p. 279. In an article in the online journal Quanta, "Time's (Almost) Irreversible Arrow" (January 7, 2016), Frank Wilczek explained the coinage as follows: "A few years before [in 1977], a supermarket display of brightly colored boxes of a laundry detergent named Axion had caught my eye. It occurred to me that 'axion' sounded like the name of a particle and really ought to be one. So when I noticed a new particle that 'cleaned up' a problem with an 'axial' current, I saw my chance. (I soon learned that Steven Weinberg had also noticed this particle, independently. He had been calling it the 'Higglet.' He graciously, and I think wisely, agreed to abandon that name.) Thus began a saga whose conclusion remains to be written."

First Known Use

1978, in the meaning defined above