Isotopic abundance refers to the relative proportions of different isotopes in a sample. There are a number of synonyms for this term that are commonly used in scientific literature. One alternative is isotopic composition, which describes the ratios of different isotopes in a sample. Isotope distribution is another phrase that is sometimes used to describe isotopic abundance. Meanwhile, isotopic ratio is a term that is often used interchangeably with isotopic abundance, since both refer to the ratios of different isotopes in a sample. Other synonyms for isotopic abundance include isotope abundance and isotopic signature. Regardless of the terminology used, isotopic abundance is a key concept in various fields of science, from geochemistry to biology.