The Avogadro constant is not the defining constant of the mole

Abstract The SI (2019) claims that the Avogadro constant N A has the same character as the other six defining constants Δ ν Cs , c, h, e, k , and K cd , and that the same approach that is used to redefine the other base units may also be used to redefine the mole based on N A . The SI (2019) states that the expression N A = 6.022 140 76 × 10 23 × mol −1 is a defining relation whose inversion provides the algebraic definition of the mole. This Letter shows that N A is not the defining constant of the mole. The unit mole is defined by the SI description of the Avogadro number { N A }.