Dehydration is a condition when the body loses more water than it takes in.

 At a dehydrated condition body does not have enough fluids to carry out bodily functions properly.

The basic causes of dehydration are not taking in enough water, loosing more water, or both.

Additional causes include diarrhea, vomiting, severe sweating as these ailments reduce water in the body.

Symptoms of dehydration include extreme thirst, dark urine, headache, muscle cramps, etc. 

Drink plenty of  water to recover the water loss from the body.