D20 water is not a term used in science. However, there is a similar term called D2O, which stands for deuterium oxide or heavy water. It is a form of water where the hydrogen atoms are replaced with deuterium, an isotope of hydrogen that contains one proton and one neutron in its nucleus. Heavy water is denser than normal water, and its chemical formula is D2O. It is used in many chemical applications, and in some nuclear reactors, it is used to slow down neutrons so that they react with fissionable 235U rather than nonfissioning 238U, thus eliminating the need for uranium enrichment. The physical properties of heavy water differ from those of normal water in several ways, such as its dissociation and ion concentration.