Hydrate, any compound containing water in the form of H2O molecules, usually, but not always, with a definite content of water by weight. The best-known hydrates are crystalline solids that lose their fundamental structures upon removal of the bound water.
Drinking enough water each day is crucial for many reasons: to regulate body temperature, keep joints lubricated, prevent infections, deliver nutrients to cells, and keep organs functioning properly. Being well-hydrated also improves sleep quality, cognition, and mood.