- either of a pair of optical isomers that are mirror images of each other.
- chem a molecule that exhibits stereoisomerism because of the presence of one or more chiral centres
- Either of two stereoisomers that are mirror images of one another but cannot be superimposed on one another and that rotate the plane of polarized light in opposite directions. Enantiomers usually behave the same chemically but differ in optical behavior and sometimes in how quickly they react with other enantiomers. Also called optical isomer enantiomorph Compare geometric isomer.