New American Oxford Dictionary
protium
pro ti um |ˈprōtēəm, ˈprōSH (ē )əm ˈproʊdiəm | ▶noun Chemistry the common, stable isotope of hydrogen, as distinct from deuterium and tritium. ORIGIN 1930s: modern Latin, from Greek prōtos ‘first. ’
Oxford Dictionary
protium
protium |ˈprəʊtɪəm | ▶noun [ mass noun ] Chemistry the common, stable isotope of hydrogen, as distinct from deuterium and tritium. ORIGIN 1930s: modern Latin, from Greek prōtos ‘first ’.
Duden Dictionary
Protium
Pro ti um Substantiv, Neutrum , das |Pr o tium |das Protium; Genitiv: des Protiums griechisch-neulateinisch leichter Wasserstoff, Wasserstoffisotop; vgl. Isotop