Lactose is a disaccharide, meaning it's made up of two simpler sugar molecules. Its chemical formula is C₁₂H₂₂O₁₁.

However, you can also write the chemical equation for the formation of lactose:

Glucose + Galactose → Lactose + H₂O

This shows that lactose is formed by the condensation reaction of glucose and galactose, with the release of a water molecule.