ˌdīəˈzōnēəm noun
( -s )
Etymology: International Scientific Vocabulary diaz- + -onium
: the univalent cation −N 2 + composed of two nitrogen atoms united to carbon in one organic radical ; especially : a cation ArN 2 + (as benzenediazonium) obtained in the form of salts by diazotizing an arylamine and used chiefly in the manufacture of azo dyes — compare diaz-