- an isotope of hydrogen, having twice the mass of ordinary hydrogen; heavy hydrogen. Symbol: D; atomic weight: 2.01; atomic number: 1.
- a stable isotope of hydrogen, occurring in natural hydrogen (156 parts per million) and in heavy water: used as a tracer in chemistry and biology. Symbol: D or ²H; atomic no: 1; atomic wt: 2.014; boiling pt: –249.7°C
1933, coined by U.S. chemist Harold C. Urey, with Modern Latin ending + Greek deuterion, neuter of deuterios “having second place,” from deuteros “second,” from duo (see two). So called because it is twice the mass of hydrogen.
- An isotope of hydrogen with one proton and one neutron in the nucleus having an atomic weight of 2.014.heavy hydrogen hydrogen-2
- An isotope of hydrogen whose nucleus has one proton and one neutron and whose atomic mass is 2. Deuterium is used widely as a tracer for analyzing chemical reactions, and it combines with oxygen to form heavy water. Also called heavy hydrogen See Note at heavy water.