atomic mass unit

noun

: a unit of mass for expressing masses of atoms, molecules, or nuclear particles equal to ¹/₁₂ the mass of a single atom of the most abundant carbon isotope 12C

called also dalton

Example Sentences

Recent Examples on the Web What’s more, the large compounds are likely fragments of even larger parent molecules that could weigh thousands of atomic mass units, Postberg says. National Geographic, 27 June 2018 Previously, Cassini detected lighter, gassy molecules such as methane and ethane, which contain one or two carbon atoms and a smattering of hydrogens; these molecules weigh in at around 15 atomic mass units. National Geographic, 27 June 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'atomic mass unit.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History

First Known Use

circa 1942, in the meaning defined above

Time Traveler
The first known use of atomic mass unit was circa 1942

Dictionary Entries Near atomic mass unit

Cite this Entry

“Atomic mass unit.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/atomic%20mass%20unit. Accessed 22 Mar. 2023.

Kids Definition

atomic mass unit

noun
: a unit of mass for expressing masses of atoms, molecules, or nuclear particles that is equal to frac::1/12 of the atomic mass of the most abundant kind of carbon

Medical Definition

atomic mass unit

noun
: a unit of mass for expressing masses of atoms, molecules, or nuclear particles equal to ¹/₁₂ the mass of a single atom of the most abundant carbon isotope 12C

called also dalton

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