: 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

Examples of neutron in a Sentence

Recent Examples on the Web
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The reactor relies on fast neutrons rather than slow thermal ones. — Aman Tripathi, Interesting Engineering, 8 Oct. 2026 And deuterium nuclei contain a neutron that can be liberated by a neutrino and then detected, regardless of the type of neutrino. — Doug Cowen, The Conversation, 8 Oct. 2026 To produce the plutonium, this process needs to be self-sustaining, meaning every neutron’s release has to trigger the release of at least one more. — Mike McRae 06, New Atlas, 6 Oct. 2026 See All Example Sentences for neutron

Word History

Etymology

probably from neutral

First Known Use

1921, in the meaning defined above

Time Traveler
The first known use of neutron was in 1921

Cite this Entry

“Neutron.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/neutron. Accessed 11 Oct. 2026.

Kids Definition

: 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

: 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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