Deuterium oxide, commonly known as heavy water, is a form of water where the hydrogen atoms are replaced with deuterium, a heavier isotope of hydrogen. This gives it unique properties, such as a higher boiling point and density compared to regular water. It is chemically similar to ordinary water but behaves differently in certain physical and chemical processes. Heavy water is primarily used in nuclear reactors as a neutron moderator, which helps sustain nuclear reactions. It is also utilized in various scientific research applications, including studies in biochemistry and nuclear physics. While it is not toxic, consuming large amounts can be harmful due to its effects on biological processes.