The Collaborative International Dictionary of English v.0.48:

Tractable \Tract"a*ble\, a. [L. tractabilis, fr, tractare to
   draw violently, to handle, treat. See Treat, v. t.]
   1. Capable of being easily led, taught, or managed; docile;
      manageable; governable; as, tractable children; a
      tractable learner.
      [1913 Webster]

            I shall find them tractable enough.   --Shak.
      [1913 Webster]

   2. Capable of being handled; palpable; practicable; feasible;
      as, tractable measures. [Obs.] --Holder.
      [1913 Webster] --Tract"a*ble*ness, n. -- Tract"a/bly,
      adv.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tractableness
    n 1: the trait of being easily persuaded [syn: tractability,
         tractableness, flexibility] [ant: intractability,
         intractableness]