https://doi.org/10.1351/goldbook.D01681
This is defined by analogy with @E02075@ as the ratio of the percentage of one @D01679@ in a mixture to that of the other.
Source:
PAC, 1996, 68, 2193. (Basic terminology of stereochemistry (IUPAC Recommendations 1996)) on page 2206 [Terms] [Paper]