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®

persuasively
     adv : in a persuasive manner; "this essay argues so
           persuasively..."