Carbohydrates which differ in configuration at the glycosidic carbon (i.e., C1 in aldoses and C2 in ketoses) are called anomers while those differ in configuration at any carbon other than glycosidic carbon are called epimers.
For example α – D glucose and β-D glucose are anomers since they differ in configuration at C1 while glucose and mannose are called epimers since they differ in configuration at C2 (other than glycosidic carbon C1). In other words glucose and mannose are C2 epimers. Similarly glucose and galactose are C4 epimers.
