Deuterated ethanol (C2D5OD)  is a form (called an isotopologue) of ethanol (C2H5OH) in which the hydrogen atom ("H") is replaced with deuterium (heavy hydrogen) isotope ("D").
Deuterated ethanol (C2D5OD) is an example of an isotopologue, which refers to a molecule with modified atomic composition, in this case, replacing hydrogen with deuterium, altering its chemical behavior and properties.