Source : Webster's Revised Unabridged Dictionary (1913)

Hypothetic \Hy`po*thet"ic\, Hypothetical \Hy`po*thet"ic*al\, a.
   [L. hypotheticus, Gr. ?: cf. F. hypoth['e]tique.]
   Characterized by, or of the nature of, an hypothesis;
   conditional; assumed without proof, for the purpose of
   reasoning and deducing proof, or of accounting for some fact
   or phenomenon.

         Causes hypothetical at least, if not real, for the
         various phenomena of the existence of which our
         experience informs us.                   --Sir W.
                                                  Hamilton.

   {Hypothetical baptism} (Ch. of Eng.), baptism administered to
      persons in respect to whom it is doubtful whether they
      have or have not been baptized before. --Hook. --
      {Hy`po*thet"ic*al*ly}, adv. --South.

Source : WordNet®

hypothetically
     adv : by hypothesis