isotopic abundance 

https://doi.org/10.1351/goldbook.I03332
The relative number of atoms of a particular isotope in a mixture of the isotope of an element, expressed as a fraction of all the atoms of the element.
Source:
PAC, 1982, 54, 1533. (Glossary of terms used in nuclear analytical chemistry (Provisional)) on page 1535 [Terms] [Paper]
Citation: 'isotopic abundance' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.I03332 RIS BibTex EndNote
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Last revised: February 24, 2014