[ter.na.ry] adj [ME, fr. L ternarius, fr. terni three each; akin to L tres three--more at three] (15c) 1 a: of, relating to, or proceeding by threes b: having three elements, parts, or divisions: threefold c: arranged in threes "~ petals"
2: using three as the base "a ~ logarithm" 3 a: being or consisting of an alloy of three elements b: of, relating to, or containing three different elements, atoms, radicals, or groups "sulfuric acid is a ~ acid"
4: third in order or rank