velocity, v,c in biotechnology, in mass transport

https://dx.doi.org/10.1351/goldbook.V06607
Vector quantity equal to the derivative of the position vector with respect to time (symbols u,v,w for components of c).
Source:
ISO 31-1: 1992 (Quantities and Units - Part 1: Space and Time.)
PAC, 1996, 68, 957 (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 997