https://doi.org/10.1351/goldbook.M03980

The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6.022 140 76 x 10E23 elementary entities. This number is the fixed numerical value of the Avogadro constant, NA, when expressed in the unit mol-1 and is called the Avogadro number.

The amount of substance, symbol n, of a system is a measure of the number of specified elementary entities. An elementary entity may be an atom, a molecule, an ion, an electron, any other particle or specified group of particles.The formulation of this definition was agreed upon by the 26

BIPM, The International System of Units, SI Brochure, 9