Is there a difference between dry skin and dehydrated skin?

Dry skin, xerosis, dried out skin and dehydrated skin is more or less the same thing. What's important to find out is why the skin is dry. We often use the term dry skin for skin that is naturally dry (people who have always had dry skin), and the term dried out or dehydrated skin for skin that becomes dry after being exposed to aggressions (winter xerosis, xerosis caused by certain products).