Dehydration is the excessive loss of body water.
Dehydration or water loss may also refer to other cases of water loss/removal (sometimes colloquially): Drying, the removal of water through chemical or physical means Desiccation, sometimes synonymous with drying, sometimes an extreme form of it Food drying, food preservation by dehydration Dehydration reaction, a chemical reaction Dryness (medical) of skin, etc.
See also Dehydrogenation