H20

H2O is the chemical formula for dihydrogen monoxide, which is water. It is the combination of two hydrogen atoms bonded to a single oxygen atom. H2O is the most abundant compound on the surface of the Earth.

Water is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of most living organisms. It is vital for all known forms of life, even though it provides no calories or organic nutrients.