quaternity

from WordNet (r) 3.0 (2006)

quaternity
    n 1: the cardinal number that is the sum of three and one [syn:
         {four}, {4}, {IV}, {tetrad}, {quatern}, {quaternion},
         {quaternary}, {quaternity}, {quartet}, {quadruplet},
         {foursome}, {Little Joe}]

from The Collaborative International Dictionary of English v.0.48

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.
      [1913 Webster]

   2. The union of four in one, as of four persons; -- analogous
      to the theological term trinity.
      [1913 Webster]