Galactose

Galactose (from the Greek stem γάλακτ– "galakt–", "milk") is a sugar. It has almost the same chemical structure as glucose. 
Large amounts of pure galactose do not exist in nature. Instead, galactose is usually found with glucose in lactose, a sugar found in milk and other milk products. After lactose is digested and absorbed, galactose arrives in the liver. There it is changed into either glucose or glycogen.