Functions of water in the body include:

1. Transport of nutrients and waste products: Water plays a crucial role in transporting nutrients and waste products throughout the body. It helps to move nutrients to the cells, and it helps to remove waste products from the body through urine and sweat.
2. Regulation of body temperature: Water helps to regulate body temperature by carrying heat away from internal organs and skin through sweat.
3. Lubrication of joints and organs: Water is an essential component of synovial fluid, which is found in the joints and helps to lubricate them. Water is also important for the production of other body fluids, such as saliva and mucus.
4. Maintenance of blood volume: Water helps to maintain blood volume, which is essential for the proper functioning of the circulatory system. Dehydration can lead to a decrease in blood volume, which can cause a drop in blood pressure.

Sources of water include:

1. Drinking water: Drinking water is the most common source of water for the body. It is recommended to drink at least 8 glasses of water per day to maintain adequate hydration.
2. Food: Many foods, especially fruits and vegetables, contain high amounts of water. For example, watermelon, cucumber, lettuce, and tomatoes are all high in water content.
3. Beverages: Other beverages, such as tea, coffee, milk, and juice, can also contribute to water intake. However, it is important to choose beverages that do not contain added sugars or other harmful additives.

In summary, water is a vital nutrient for the human body that is necessary for many important functions, including the transport of nutrients and waste products, regulation of body temperature, lubrication of joints and organs, and maintenance of blood volume. It is important to ensure adequate hydration by consuming water and other sources of fluids regularly throughout the day.