relative viscosity

Synonym: viscosity ratio
https://doi.org/10.1351/goldbook.R05282
The ratio of the
viscosity
of the solution, η, to the
viscosity
of the solvent, ηs, i.e. ηr=ηηs. Synonymous with viscosity ratio.
Source:
Purple Book, 1st ed., p. 62 [Terms] [Book]