: an uncharged elementary particle that has a mass nearly equal to that of the proton and is present in all known atomic nuclei except the hydrogen nucleus
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Its lack of interaction with light means it can't be composed of protons, neutrons and electrons — the particles that compose atoms.
—
Robert Lea, Space.com, 15 May 2026
Building a Treasure Map Helium-3 is an isotope of helium that possesses one fewer neutron than its run-of-the-mill counterpart, helium-4, which is the only other stable helium isotope.
—Robin George Andrews, Scientific American, 14 May 2026
Called Super Safe, Small and Simple, or 4S reactor, the design features a fast neutron microreactor cooled by liquid sodium.
—Ameya Paleja, Interesting Engineering, 7 May 2026
Another experimental variation in 2016 involved replacing the electron with a muon in a deuterium atom—a heavier isotope of hydrogen, with a neutron as well as a proton and an electron.
—ArsTechnica, 14 Apr. 2026
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Robert Lea, Space.com, 15 May 2026
Building a Treasure Map Helium-3 is an isotope of helium that possesses one fewer neutron than its run-of-the-mill counterpart, helium-4, which is the only other stable helium isotope.
—Robin George Andrews, Scientific American, 14 May 2026
Called Super Safe, Small and Simple, or 4S reactor, the design features a fast neutron microreactor cooled by liquid sodium.
—Ameya Paleja, Interesting Engineering, 7 May 2026
Another experimental variation in 2016 involved replacing the electron with a muon in a deuterium atom—a heavier isotope of hydrogen, with a neutron as well as a proton and an electron.
—ArsTechnica, 14 Apr. 2026
See All Example Sentences for neutron
Cite this Entry
“Neutron.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/neutron. Accessed 20 May. 2026.
Copy CitationKids Definition
neutron
noun
neu·tron
ˈn(y)ü-ˌträn 
: an uncharged atomic particle that has a mass nearly equal to that of the proton and is present in all known atomic nuclei except the hydrogen nucleus
Medical Definition
neutron
noun
neu·tron
ˈn(y)ü-ˌträn
: an uncharged elementary particle that has a mass nearly equal to that of the proton and is present in all known atomic nuclei except the hydrogen nucleus
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