friction factor, μ in polymer chemistry

https://dx.doi.org/10.1351/goldbook.F02530
Quotient of frictional force and normal force, for a sliding body. Formerly called frictional coefficient or coefficient of friction.
Source:
PAC, 1996, 68, 957 (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 974