= Molecular count and amount of substance
{title2=$N=nN_{\mathrm A}$}
The molecular count $N$ is a dimensionless integer; the <amount of substance> $n$ has unit <mole>, symbol $\mathrm{mol}$. They satisfy
$$
N=nN_{\mathrm A},\qquad N_{\mathrm A}=6.02214076\times10^{23}\,\mathrm{mol}^{-1}.
$$
The <Avogadro constant> is exact by the modern definition of the <mole>: see https://www.bipm.org/en/si-base-units/mole[BIPM, SI base unit: mole]. Thus two <water> <molecules> correspond to $2/N_{\mathrm A}$ <moles>, whereas two <moles> of <water> contain $1.204428152\times10^{24}$ <molecules>. A <mole> is a unit for counting specified entities, which may also be <chemical atoms>, <ions> or <Electrons>.
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