What is another word for "ternion"?

Roget's Thesaurus (1911) lists these synonyms for "ternion": cube, leash, power, root, shamrock, ternary, tertiary, third, three, tierce, trefoil, trey, triad, triangle, trident, triform, trigon, trinal, trinity, trinomial, trio, triple, triplet, tripod, trireme, triskele, triskelion, triune, triunity.