determiner

from WordNet (r) 3.0 (2006)

determiner
    n 1: an argument that is conclusive [syn: {clincher},
         {determiner}, {determining factor}]
    2: one of a limited class of noun modifiers that determine the
       referents of noun phrases [syn: {determiner},
       {determinative}]
    3: a determining or causal element or factor; "education is an
       important determinant of one's outlook on life" [syn:
       {determinant}, {determiner}, {determinative}, {determining
       factor}, {causal factor}]

from The Collaborative International Dictionary of English v.0.48

Determiner \De*ter"min*er\, n.
   One who, or that which, determines or decides.
   [1913 Webster]