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.