Source : Webster's Revised Unabridged Dictionary (1913)

Quaternity \Qua*ter"ni*ty\, n. [LL. quaternitas, fr. L. quaterni
   four each: cf. F. quaternit['e].]
   1. The number four. [Obs.] --Sir T. Browne.

   2. The union of four in one, as of four persons; -- analogous
      to the theological term trinity.

Source : WordNet®

quaternity
     n : the cardinal number that is the sum of three and one [syn: {four},
          {4}, {IV}, {tetrad}, {quatern}, {quaternion}, {quaternary},
          {quartet}, {quadruplet}, {foursome}, {Little Joe}]