Number of defined particles, or elementary entities of a defined component, crossing a cross-section divided by the time.
See: mass flow rate, volume flow rate
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)