What kind of condition is dehydration or "behind in fluids"?

Dehydration: Living things including people, plants and animals by living process foods and produce water, but also excrete water through the skin or other outer membranes. If the water intake doesn't keep up with the need the living things get dehydrated. Fever and disease can increase the water requirements.

Less fluid: Dehydration occurs when less fluid than necessary for the body are ingested and/or fluids are lost faster than a person can replace them. Examples include when a person has severe nausea and vomiting and is losing fluid via vomiting and cannot drink enough to replace these fluids due to nausea. Sometimes, fluids need to be replaced intravenously in this situation.