enantiomer excess (enantiomeric excess) 

Also contains definition of: percent enantiomer excess
https://doi.org/10.1351/goldbook.E02070
For a mixture of (+)- and (−)-enantiomers, with composition given as the mole or weight fractions F(+) and F(−) (where F(+)+F(−)=1) the enantiomer excess is defined as |F(+)−F(−)| (and the percent enantiomer excess by 100 |F(+)−F(−)|). Frequently this term is abbreviated as e.e.
See: optical purity
Source:
PAC, 1996, 68, 2193. (Basic terminology of stereochemistry (IUPAC Recommendations 1996)) on page 2207 [Terms] [Paper]
Citation: 'enantiomer excess' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.E02070 RIS BibTex EndNote
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Last revised: February 24, 2014