Water makes up about 60% of an adult's body weight and is essential for life. It transports nutrients and waste, maintains body structures, and enables metabolic processes. The body loses water through urine, sweat, and breathing and must replenish it through drinking water and other beverages as well as water in foods. Dehydration can develop if water intake is inadequate while overconsumption of water can cause water intoxication. Adults should aim to drink around 8-12 cups of total water per day from all sources to maintain proper hydration.