Source : Webster's Revised Unabridged Dictionary (1913)

Affirmative \Af*firm"a*tive\, n.
   1. That which affirms as opposed to that which denies; an
      affirmative proposition; that side of question which
      affirms or maintains the proposition stated; -- opposed to
      {negative}; as, there were forty votes in the affirmative,
      and ten in the negative.

            Whether there are such beings or not, 't is
            sufficient for my purpose that many have believed
            the affirmative.                      --Dryden.

   2. A word or phrase expressing affirmation or assent; as,
      yes, that is so, etc.

Affirmative \Af*firm"a*tive\, a. [L. affirmativus: cf. F.
   affirmatif.]
   1. Confirmative; ratifying; as, an act affirmative of common
      law.

   2. That affirms; asserting that the fact is so; declaratory
      of what exists; answering ``yes'' to a question; --
      opposed to {negative}; as, an affirmative answer; an
      affirmative vote.

   3. Positive; dogmatic. [Obs.] --J. Taylor.

            Lysicles was a little by the affirmative air of
            Crito.                                --Berkeley.

   4. (logic) Expressing the agreement of the two terms of a
      proposition.

   5. (Alg.) Positive; -- a term applied to quantities which are
      to be added, and opposed to {negative}, or such as are to
      be subtracted.

Source : WordNet®

affirmative
     adj 1: affirming or giving assent; "an affirmative decision";
            "affirmative votes"; "an affirmative nod"; "an
            affirmatory gesture" [syn: {affirmatory}] [ant: {negative}]
     2: expecting the best; "an affirmative outlook" [syn: {optimistic}]
     3: supporting a policy or attitude etc; "an affirmative
        argument" [syn: {favoring}]

affirmative
     n : a reply of affirmation; "he answered in the affirmative"
         [ant: {negative}]