b. In later use prefixed to the names of complex radicals or compounds, signifying that the whole complex is present thrice over, and not merely the single element or radical immediately following the prefix; e.g. trisbenzene-azophenol, C6H2(N:NC6H5)3OH, a compound containing three N:NC6H5 groups substituted in phenol, C6H5OH; tristhio-dimethyl-benzaldehyde, {C6H3(CH3)2.CHS}3, in which the whole group is present thrice.