Source : Webster's Revised Unabridged Dictionary (1913)

Persuasive \Per*sua"sive\, n.
   That which persuades; an inducement; an incitement; an
   exhortation. -- {Per*sua"sive*ly}, adv. --
   {Per*sua"sive*ness}, n.

Source : WordNet®

persuasiveness
     n : the power to induce the taking of a course of action or the
         embracing of a point of view by means of argument or
         entreaty; "the strength of his argument settled the
         matter" [syn: {strength}] [ant: {unpersuasiveness}]