What is the chemical symbol for water?

The chemical symbol for water is represented as H2O. This notation indicates that each molecule of water is composed of two hydrogen atoms and one oxygen atom. The 'H' stands for hydrogen, and the 'O' stands for oxygen, with the subscript '2' indicating the number of hydrogen atoms present in the molecule. This combination results in water, a vital substance for all known forms of life.

The other options provided represent different chemical compounds. O2 is the symbol for oxygen gas, which consists of two oxygen atoms and is essential for respiration in many living organisms but is not water. CO2 stands for carbon dioxide, a gas that is a product of respiration and combustion and plays a crucial role in photosynthesis. HO2 is a less common notation that refers to a hypothetical or less stable molecule rather than the widely recognized formula for water. Thus, H2O is the only correct representation for water.