Epimer

In chemistry epimers are stereoisomers that differ in configuration of only one stereogenic center. All other stereocenters in the molecules, if any, are the same in each. Thus epimeric molecules can be either enantiomers or diastereomers of each other depending on whether there are stereocenters in addition to the epimeric one.

In chemical nomenclature, one of the epimeric pairs is given the prefix epi- for example in quinine and epi-quinine. When the pairs are enantiomers, the prefix becomes ent-.