The term
stable isotope has a similar meaning to
stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form
stable isotopes usually refers to isotopes of the same element. The relative abundance of such stable isotopes can be measured experimentally (
isotope analysis), yielding an isotope ratio that can be used as a research tool. Theoretically, such stable isotopes could include the radiogenic daughter products of radioactive decay, used in
radiometric dating. However, the expression
stable isotope ratio is preferably used to refer to isotopes whose relative abundances are affected by
isotope fractionation in nature. This field is termed
stable isotope geochemistry.