Is it ensure, insure, or assure?
1802, "compound of water and another chemical," from French hydrate, coined c.1800 by French chemist Joseph-Louis Proust (1754-1826) from Greek hydr-, stem of hydor "water" (see water (n.1)).
hydrate hy·drate (hī'drāt')
A solid compound containing water molecules combined in a definite ratio as an integral part of a crystal. v. hy·drat·ed, hy·drat·ing, hy·drates
To supply water to a person or thing in order to restore or maintain fluid balance.
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. Exceptions to this are the zeolites (aluminum silicate minerals or their synthetic analogues that contain water in indefinite amounts) as well as similar clay minerals, certain clays, and metallic oxides, which have variable proportions of water in their hydrated forms; zeolites lose and regain water reversibly with little or no change in structure