mole ratio

symbol: $r$
synonym: amount ratio
https://doi.org/10.1351/goldbook.15341
Amount of one constituent divided by the amount of a second constituent in the same system. For constituents 1 and 2, \[r_{12} = n_{1}/n_{2}\]
Source:
PAC, 2008, 80, 233. (Glossary of terms related to solubility (IUPAC Recommendations 2008)) on page 255 [Terms] [Paper]