deuterium

noun

deu·​te·​ri·​um dü-ˈtir-ē-əm How to pronounce deuterium (audio)
also dyü-
: an isotope of hydrogen that has one proton and one neutron in its nucleus and that has twice the mass of ordinary hydrogen
—symbol D

called also heavy hydrogen

Examples of deuterium in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
The unexpected discovery of a methanol molecule containing deuterium was made in the planet-forming disk around only one of those 11 stars, namely the young star IRAS 4A2, located about a thousand light-years away in the Perseus Molecular Cloud. — Keith Cooper, Space.com, 15 Oct. 2026 Mainstream projects use two heavy hydrogen isotopes called deuterium and tritium. — Aman Tripathi, Interesting Engineering, 2 Oct. 2026 Our work explained how making a minor modification to a reacting molecule – switching the hydrogen to deuterium – could increase the size of the energy barrier and stop tunneling. — Sophya Garashchuk, The Conversation, 1 Oct. 2026 See All Example Sentences for deuterium

Word History

Etymology

New Latin, from Greek deuteros second

First Known Use

1933, in the meaning defined above

Time Traveler
The first known use of deuterium was in 1933

Phrases Containing deuterium

Rhymes for deuterium

See All Rhymes for deuterium

Browse Nearby Words

deuteride
deuterium
deuterium oxide
See all Nearby Words

Cite this Entry

“Deuterium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/deuterium. Accessed 20 Oct. 2026.

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Kids Definition

deuterium

noun
deu·​te·​ri·​um d(y)ü-ˈtir-ē-əm How to pronounce deuterium (audio)
: the hydrogen isotope that is twice the mass of ordinary hydrogen

called also heavy hydrogen

Medical Definition

deuterium

noun
deu·​te·​ri·​um d(y)ü-ˈtir-ē-əm How to pronounce deuterium (audio)
: an isotope of hydrogen that has one proton and one neutron in its nucleus and that has twice the mass of ordinary hydrogen

called also heavy hydrogen

More from Merriam-Webster on deuterium

Britannica.com: Encyclopedia article about deuterium

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