mass number


Definition of mass number

: an integer that approximates the mass of an isotope and designates the number of nucleons in the nucleus

Examples of mass number in a Sentence

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An initial look at comments supporting the blackout repeal didn’t indicate similar issues with fake names or mass numbers of identical letters. Paul Overberg, WSJ, "The NFL’s Other Problem: Fake Fans Lobbying for the Blackout," 7 Sep. 2018

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

First Known Use of mass number

1923, in the meaning defined above

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The first known use of mass number was in 1923

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mass number


Medical Definition of mass number

: an integer that approximates the mass of an isotope and that designates the number of nucleons in the nucleus the symbol for carbon of mass number 14 is 14C or C14 — compare atomic mass

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incapable of being surmounted or overcome

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