D⁻ is a notation used in various scientific fields, particularly in chemistry and physics, to represent a negatively charged ion or particle. The "D" typically refers to deuterium, an isotope of hydrogen that contains one proton and one neutron in its nucleus. The negative charge indicates that the particle has gained an extra electron, resulting in a stable ion. In the context of nuclear reactions or particle physics, D⁻ can also refer to a specific type of particle that plays a role in certain interactions. Understanding D⁻ is important for studying isotopes, nuclear fusion, and other phenomena related to atomic structure and behavior.