https://doi.org/10.1351/goldbook.M03980
The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly elementary entities. This number is the fixed numerical value of the Avogadro constant, , when expressed in the unit and is called the Avogadro number.
The amount of substance, symbol Note: The formulation of this definition was agreed upon by the 26th CGPM in November 2018 with effect from 20 May 2019.