https://doi.org/10.1351/goldbook.I03033

The ratio of the natural logarithm of the relative viscosity, η r, to the mass concentration of the polymer, c, i.e. \[\eta _{\text{inh}}\equiv \eta _{\ln} = \frac{\ln \eta _{\text{r}}}{c}\] The quantity η ln, with which the inherent viscosity is synonymous, is the logarithmic viscosity number.**Notes: **

*Source: *

Purple Book, 1st ed., p. 63 (http://old.iupac.org/publications/books/author/metanomski.html)

- The unit must be specified; \(\text{cm}^{3}\ \text{g}^{-1}\) is recommended.
- These quantities are neither viscosities nor pure numbers. The terms are to be looked on as traditional names. Any replacement by consistent terminology would produce unnecessary confusion in the polymer literature.

Purple Book, 1st ed., p. 63 (http://old.iupac.org/publications/books/author/metanomski.html)