the.com/mole fraction

means Mole fraction is the ratio of the number of moles of one component to the total number of moles in a mixture — a way to express composition purely by particle count, not mass or volume.

from The word 'mole' here traces back to the German 'Mol,' shortened from 'Molekül' (molecule), coined in the late 19th century by chemist Wilhelm Ostwald as a unit for 'amount of substance.' 'Fraction' is the ordinary Latin-rooted word for a part of a whole, from 'frangere,' to break. Put together, 'mole fraction' is a 20th-century chemistry term — once Avogadro's number gave chemists a way to count particles instead of weigh them, they needed a ratio that broke a mixture down the same way, piece by piece rather than gram by gram.