Anhydrate refers to a chemical compound that lacks water molecules. The opposite of anhydrate is hydrate, which refers to a compound that has water molecules in its crystal structure. For example, copper sulfate anhydrate is a white powder, whereas copper sulfate pentahydrate has five water molecules and appears as blue crystals. Another antonym for anhydrate is saturated, which means a solution or substance has reached a point of maximum concentration and cannot dissolve any more solute. A related antonym for anhydrate is desiccate, which means to remove water from something, often by drying or dehydration.