neutron

American  

[noo-tron, nyoo-] / ˈnu trɒn, ˈnju- /

noun

Physics.

• neutrons
  plural

1. an elementary particle having no charge, mass slightly greater than that of a proton, and spin of ½: a constituent of the nuclei of all atoms except those of hydrogen. n

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neutron British  

/ ˈnjuːtrɒn /

noun

1. physics a neutral elementary particle with a rest mass of 1.674 92716 × 10 ^–27 kilogram and spin 1/ 2 ; classified as a baryon. In the nucleus of an atom it is stable, but when free it decays

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neutron Scientific  

/ no̅o̅′trŏn′ /

1. An electrically neutral subatomic particle in the baryon family, having a mass of 1.674 × 10 ^{- 24} grams (1,838 times that of the electron and slightly greater than that of the proton). Neutrons are part of the nucleus of all atoms, except hydrogen, and have a mean lifetime of approximately 1.0×10 ³ seconds as free particles. They consist of a triplet of quarks, including two down quarks and one up quark, bound together by gluons. In radioactive atoms, excess neutrons are converted to protons by beta decay. Beams of neutrons from nuclear reactors are used to bombard the atoms of various elements to produce fission and other nuclear reactions and to determine the atomic arrangements in molecules.

2. See Table at subatomic particle

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neutron Cultural  

1. An elementary particle without an electrical charge; one of the building blocks of the nucleus of the atom. A neutron has about the same mass as a proton.

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Other Word Forms

Noun Inflected Forms

• neutrons
  plural

Etymology

Origin of neutron

First recorded in 1920–25; neutr(o)- + -on ¹

Explanation

The nucleus of an atom includes a proton, which has a positive charge, and a neutron, which has no charge, or is "neutral." The hydrogen atom is the only atom without a neutron. The basis for the word neutron is both "neutral" and the suffix "-on," which probably comes from the Greek ión, "to go." The word ion first appeared in English in 1834, and neutron appeared in 1921, to represent the neutral part of an atom. Don't let the "neutral" part fool you, though — a neutron bomb, while "smaller" than other nuclear weapons, is still capable of mass destruction, as it emits more radiation, causing a wider sweep of damage to life.

Example Sentences

See Examples For:

neutron neutrons

Researchers, including Dr. Marcus Lower from Swinburne University of Technology, investigated this long-standing quantum mystery by studying a magnetar, a rare type of neutron star that possesses the strongest magnetic fields known in the universe.

From Science Daily ● Aug. 18, 2026

Similar effects already help stabilize dense objects such as white dwarfs and neutron stars and can reproduce the inflationary expansion phase.

From Science Daily ● Aug. 11, 2026

By combining thermal conductivity measurements with neutron scattering data, the team was able to directly connect the dramatic increase in heat flow to changes in the atomic vibrations inside the crystal.

From Science Daily ● Jul. 11, 2026

These enormous explosions generate the energy needed to produce heavy atomic nuclei through a process known as rapid neutron capture, or the r-process.

From Science Daily ● Jul. 8, 2026

During a May conference at Caltech honoring the visiting Niels Bohr, he alluded to the lightweight neutron while describing the disintegration of eight heavy targets, up to aluminum, by deuton bombardment.

From "Big Science" by Michael Hiltzik

It reflects how protons and neutrons are arranged and can provide valuable information about the strong force - one of nature's four fundamental forces, which scientists are still working to fully understand.

From Science Daily ● Aug. 23, 2026

In this case, the neutrons and protons in the nucleus essentially flipped their internal magnets.

From Science Daily ● Aug. 21, 2026

That distance was too great for the instrument to detect gamma rays coming from the planet, but scientists believed it might still register neutrons escaping from the Martian surface and atmosphere.

From Science Daily ● Jul. 28, 2026

Helium-3 is an isotope of helium, defined by the number of neutrons in the atom's nucleus.

From BBC ● Jun. 16, 2026

Rutherford and Chadwick stated flatly that they had not found Lawrence’s suspiciously light neutrons in any of their bombardments and saw no reason to revise their calculation of the neutron’s weight to conform to Lawrence’s.

From "Big Science" by Michael Hiltzik