Source : Webster's Revised Unabridged Dictionary (1913)

Determinative \De*ter"mi*na*tive\, a. [Cf. F. d['e]terminatif.]
   Having power to determine; limiting; shaping; directing;
   conclusive.

         Incidents . . . determinative of their course. --I.
                                                  Taylor.

   {Determinative tables} (Nat. Hist.), tables presenting the
      specific character of minerals, plants, etc., to assist in
      determining the species to which a specimen belongs.

Determinative \De*ter"mi*na*tive\, n.
   That which serves to determine.

         Explanatory determinatives . . . were placed after
         words phonetically expressed, in order to serve as an
         aid to the reader in determining the meaning. --I.
                                                  Taylor (The
                                                  Alphabet).

Source : WordNet®

determinative
     adj : having the power or quality of deciding; "the crucial
           experiment"; "cast the deciding vote"; "the
           determinative (or determinant) battle" [syn: {crucial},
            {deciding(a)}, {determinant}, {determining(a)}]
     n 1: one of a limited class of noun modifiers that determine the
          referents of noun phrases [syn: {determiner}]
     2: a determining or causal element or factor; "education is an
        important determinant of one's outlook on life" [syn: {determinant},
         {determiner}, {determining factor}, {causal factor}]