Source : Webster's Revised Unabridged Dictionary (1913)

Tenability \Ten`a*bil"i*ty\, n.
   The quality or state of being tenable; tenableness.

Source : WordNet®

tenability
     n : the quality of being plausible or acceptable to a reasonable
         person; "he questioned the tenability of my claims" [syn:
          {reasonableness}, {tenableness}]