Source : Webster's Revised Unabridged Dictionary (1913)

Determinant \De*ter"mi*nant\, a. [L. determinans, p. pr. of
   determinare: cf. F. d['e]terminant.]
   Serving to determine or limit; determinative.

Determinant \De*ter"mi*nant\, n.
   1. That which serves to determine; that which causes
      determination.

   2. (Math.) The sum of a series of products of several
      numbers, these products being formed according to certain
      specified laws;

   Note: thus, the determinant of the nine numbers a, b, c,a',
         b', c',a'', b'', c'', is a b' c'' - a b'' c' + a' b''
         c] - a' b c'' + a'' b' c. The determinant is written by
         placing the numbers from which it is formed in a square
         between two vertical lines. The theory of determinants
         forms a very important branch of modern mathematics.

   3. (Logic) A mark or attribute, attached to the subject or
      predicate, narrowing the extent of both, but rendering
      them more definite and precise. --Abp. Thomson.

Source : WordNet®

determinant
     adj : having the power or quality of deciding; "the crucial
           experiment"; "cast the deciding vote"; "the
           determinative (or determinant) battle" [syn: {crucial},
            {deciding(a)}, {determinative}, {determining(a)}]
     n 1: a determining or causal element or factor; "education is an
          important determinant of one's outlook on life" [syn: {determiner},
           {determinative}, {determining factor}, {causal factor}]
     2: a square matrix used to solve simultaneous equations