ternion

from WordNet (r) 3.0 (2006)

ternion
    n 1: the cardinal number that is the sum of one and one and one
         [syn: {three}, {3}, {III}, {trio}, {threesome}, {tierce},
         {leash}, {troika}, {triad}, {trine}, {trinity}, {ternary},
         {ternion}, {triplet}, {tercet}, {terzetto}, {trey}, {deuce-
         ace}]

from The Collaborative International Dictionary of English v.0.48

Ternion \Ter"ni*on\, n. [L. ternio, fr. terni three each. See
   {Tern}, a.]
   The number three; three things together; a ternary. --Bp.
   Hall.
   [1913 Webster]