https://doi.org/10.1351/goldbook.A00296

Amount of a constituent divided by the total amount of all constituents in the mixture. It is also called mole fraction. Amount fraction is equal to the number fraction: the number of entities of one constituent divided by the total number of entities in the mixture.*See also:* fraction*Source: *

Green Book, 2^{nd} ed., p. 41 (https://dev.goldbook.iupac.org/files/pdf/green_book_2ed.pdf)

Green Book, 2