Dehydration is what happens when something has water removed from it. Dehydration makes people extremely thirsty, and it can make plants grow droopy and brown.

During dehydration, moisture is lost without being replaced. In humans, dehydration can happen during strenuous exercise or in extreme heat — or simply when someone doesn't drink enough water for a certain length of time. A grape becomes a raisin through dehydration, shriveling and drying as moisture is removed. Dehydration and dehydrate, first used only by scientists, have a Greek root, hydro, "water."

Definitions of dehydration
  1. noun
    the process of extracting moisture
    synonyms: desiccation, drying up, evaporation
    see moresee less
    freeze-drying, lyophilisation, lyophilization
    a method of drying food or blood plasma or pharmaceuticals or tissue without destroying their physical structure; material is frozen and then warmed in a vacuum so that the ice sublimes
    the process of thickening by dehydration
    type of:
    the process of obtaining something from a mixture or compound by chemical or physical or mechanical means
  2. noun
    dryness resulting from the removal of water
    synonyms: desiccation
    see moresee less
    type of:
    dryness, waterlessness, xerotes
    the condition of not containing or being covered by a liquid (especially water)
  3. noun
    depletion of bodily fluids
    see moresee less
    type of:
    thirst, thirstiness
    a physiological need to drink
Word Family

Test prep from the experts

Boost your test score with programs developed by’s experts.

  • Proven methods: Learn faster, remember longer with our scientific approach.
  • Personalized plan: We customize your experience to maximize your learning.
  • Strategic studying: Focus on the words that are most crucial for success.


  • Number of words: 500+
  • Duration: 8 weeks or less
  • Time: 1 hour / week


  • Number of words: 500+
  • Duration: 10 weeks or less
  • Time: 1 hour / week


  • Number of words: 700+
  • Duration: 10 weeks
  • Time: 1 hour / week