Source : Webster's Revised Unabridged Dictionary (1913)

Validity \Va*lid"i*ty\, n. [Cf. F. validit['e], L. validitas
   strength.]
   1. The quality or state of being valid; strength; force;
      especially, power to convince; justness; soundness; as,
      the validity of an argument or proof; the validity of an
      objection.

   2. (Law) Legal strength, force, or authority; that quality of
      a thing which renders it supportable in law, or equity;
      as, the validity of a will; the validity of a contract,
      claim, or title.

   3. Value. [Obs.] ``Rich validity.'' --Shak.

Source : WordNet®

validity
     n 1: the quality of being logically valid [syn: {cogency}, {rigor},
           {rigour}]
     2: the quality of having legal force or effectiveness [syn: {validness}]