## number content, $$\frac{N_{\text{B}}}{m}$$

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 (https://doi.org/10.1351/pac199668040957)