Vector quantity equal to the derivative of the position vector with respect to time (symbols \(u\), \(v\), \(w\) for components of \(c\)).
Sources: Green Book, 2nd ed., p. 11 [Terms] [Book] ISO 31-1: 1992 [Terms] [Book] PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 997 [Terms] [Paper]