1. Proceeding by threes; consisting of three; as, the ternary number was anciently esteemed a symbol of perfection, and held in great veneration.
2. (Science: chemistry) Containing, or consisting of, three different parts, as elements, atoms, groups, or radicals, which are regarded as having different functions or relations in the molecule; thus, sodic hydroxide, NaOH, is a ternary compound.
Origin: L. Ternarius, fr. Terni. See Tern.