Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71% of the Earth’s surface. It is found mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor, clouds, and precipitation.
The Ancient Greek philosopher Empedocles held that water is one of the four classical elements along with fire, earth and air, and was regarded as the basic substance of the universe. Water is also one of the five elements in traditional Chinese philosophy, along with earth, fire, wood, and metal.
All known forms of life depend on water, with many distinct properties that are critical for the proliferation of life that set it apart from other substances. It carries out this role by allowing organic compounds to react in ways that ultimately allow replication. Water is vital both as a solvent in which many of the body’s solutes dissolve and as an essential part of many metabolic processes within the body.
Civilization has historically flourished around rivers and major waterways. Large cities like London, Montreal, Paris, New York City and Hong Kong owe their success in part to their easy accessibility via water and the resultant expansion of trade. In places such as North Africa and the Middle East, where water is more scarce, access to clean drinking water was and is a major factor in human development.
Water is considered a purifier in most religions. Major faiths that incorporate ritual washing include Hinduism, Rastafarianism, Taoism, and Judaism. Immersion of a person in water is a central sacrament of Christianity, where it is called baptism. In addition, a ritual bath in pure water is performed for the dead in many religions including Judaism and Islam.
Water is often believed to have spiritual powers. In Celtic mythology, Sulis is the local goddess of thermal springs. In Hinduism, the Ganges is also personified as a goddess, while Saraswati have been referred to as goddess in Vedas. Alternatively, gods can be patrons of particular springs, rivers, or lakes. In Islam, not only does water give life, but every life is itself made of water.