Synonyms for Trio (same or very similar meaning)
WordNet sense 1 (the cardinal number that is the sum of one and one and one):
leash, ternary, three, trey, triad, trinity, triplet, troika, deuce-ace, III, tercet, ternion, terzetto, tierce, trine
WordNet sense 2 (a set of three similar things considered as a unit):
triple
From the ODE community, based on WordNet
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