a compound formed by the union of water with some other substance, generally forming a neutral body, as certain crystallized salts.-a substance which does not contain water as such, but has its constituents (hydrogen, oxygen, hydroxyl) so arranged that water may be eliminated; hence, a derivative of, or compound with, hydroxyl; hydroxide; as, ethyl hydrate, or common alcohol; calcium hydrate, or slaked lime.-to form into a hydrate; to combine with water.