mole

https://doi.org/10.1351/goldbook.M03980
The mole, symbol mol, is the SI unit of @A00297@. One mole contains exactly \(6.022\ 140\ 76 \times 10^{23}\) elementary entities. This number is the fixed numerical value of the @A00543@, \(N_{\text{A}}\), when expressed in the unit \(\text{mol}^{\text{-1}}\), and is called the Avogadro number.
The @A00297@, 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.
Note:
The formulation of this definition was agreed upon by the 26th CGPM in November 2018 with effect from 20 May 2019.
Source:
BIPM, The International System of Units, SI Brochure, 9th ed. (2019), p. 134 [Terms] [Book]