Isomer different in position for -H and -OH at 2nd, 3rd and 4th carbon atom of glucose are called as-

Epimerism (Diastereoisomerism) - When sugars are different from one another, only in configuration with regard to a single carbon atom, other than the reference carbon atom, they are called epimers. Epimers of glucose-a) 2nd Epimer of Glucose - Mannoseb) 3rd Epimer of Glucose - Allosec) 4th Epimer of Glucose - Galactose