neutron

Etymology

It is formed from English neutral + -on,^{[2][3][4][5][6]} after electron and proton.^[2][7][8] Klein takes it directly from Latin neuter (“neither”), on the analogy of electron.^[9] Etymonline says that the American chemist William D. Harkins coined the word in 1921;^[4] Barnhart credits the British physicist Ernest Rutherford, and notes that Harkins used it in 1921, probably as an independent coinage, for other meanings such as "hydrogen atom" or "one proton and one electron".^[7] The word had been formed earlier too: in 1899 William Sutherland named a hypothetical neutral pairing of a negative and a positive electron a neutron.^[2][7] It is related to neutral.^[2][9]

Earliest recorded meaning

A neutral particle consisting of a negative electron and a positive electron linked together: 1899, in W. Sutherland's article in the Philosophical Magazine, a sense now obsolete.^[2][7] The modern sense, an uncharged subatomic particle in the atomic nucleus, is recorded from 1921, in W. D. Harkins in the same journal.^[2][10][4]

Semantic evolution

Before the modern particle, neutron was used in 1912 for a neutral atom left unstable by radioactivity, so that it could easily be ionized; this sense is now disused.^[2] The particle of 1921 remained hypothetical until the British physicist James Chadwick discovered it in 1932.^[7][9] Compounds followed: neutron star, a star made of densely packed neutrons, originally hypothetical, is recorded from 1934, and neutron bomb, a weapon that releases many lethal neutrons with little blast, from 1960.^[4]

Timeline

• 1899 – a neutral pair of a negative and a positive electron (obsolete).^[2][7]
• 1912 – an unstable neutral atom (disused).^[2]
• 1921 – the uncharged particle of the atomic nucleus.^[2][10][4]
• 1932 – the particle discovered by Chadwick.^[7][9]
• 1934 – neutron star.^[4]
• 1960 – neutron bomb.^[4]

Meanings

Noun

1. (physics) An electrically neutral elementary particle with a mass slightly greater than that of the proton, present in every atomic nucleus except that of ordinary hydrogen; it is stable in the nucleus but decays when free.^{[10][8][2][5]}
2. (obsolete) A neutral particle made up of a negative and a positive electron linked together.^[2][7]

Word family

• neutronic
• antineutron
• photoneutron
• neutron bomb
• neutron number
• neutron star
• thermal neutron
• neutron activation analysis

Related words

• neutrino
• neutral
• neuter
• electron
• proton

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
4. ^ a b c d e f g Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
5. ^ a b Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
6. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
7. ^ a b c d e f g h Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
8. ^ a b Collins English Dictionary (2023), Glasgow: HarperCollins
9. ^ a b c d Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
10. ^ a b c Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster