number content

symbol: $\frac{N_{\rm{B}}}{m}$
https://doi.org/10.1351/goldbook.N04261
Number of defined particles, or elementary entities, of a component in a system divided by the mass of that system.
Source:
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 984 [Terms] [Paper]