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

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Etymology

Origin of neutron

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

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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

The smaller companion moves rapidly around the much heavier neutron star, creating detectable changes in the light reaching Earth.

From Science Daily ● Oct. 10, 2026

These systems contain a neutron star, the extraordinarily dense remnant of a massive star, that spins rapidly while stripping material from a much smaller companion.

From Science Daily ● Oct. 10, 2026

"By revealing this previously hidden soft X-ray phase, Einstein Probe opens a new window for studying neutron star merger remnants and may ultimately help constrain the neutron star equation-of-state."

From Science Daily ● Oct. 8, 2026

"This discovery extends our view of neutron star mergers beyond the brief gamma-ray flash," said Yin.

From Science Daily ● Oct. 8, 2026

A collapsing star twice as massive as the Sun will become a supernova and then a neutron star.

From "Cosmos" by Carl Sagan

In nuclear physics, criticality refers to the point at which a chain reaction becomes self-sustaining, with each generation of fission reactions producing enough neutrons to maintain the next.

From Science Daily ● Oct. 16, 2026

The researchers also examined whether German scientists could have avoided the heavy water shortage by using graphite, a form of carbon that can also slow neutrons in nuclear reactors.

From Science Daily ● Oct. 16, 2026

This primordial material existed for only a few millionths of a second before cooling rapidly, allowing quarks and gluons to combine into protons, neutrons, and other particles found throughout the universe today.

From Science Daily ● Oct. 6, 2026

Once X-ray imaging had exposed evidence of the fossilized blood vessels, the researchers turned to neutrons in hopes of finding additional clues from the vessels and other soft tissues.

From Science Daily ● Sep. 24, 2026

The yield was two alpha particles, each with two protons and two neutrons.

From "Big Science" by Michael Hiltzik

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