isotopic abundance

https://doi.org/10.1351/goldbook.I03332
The relative number of atoms of a particular @I03331@ in a mixture of the @I03331@ 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]