The Collaborative International Dictionary of English v.0.48:

Contribute \Con*trib"ute\, v. t. [imp. & p. p. Contributed; p.
   pr. & vb. n. Contributing.] [L. contributus, p. p. of
   contribuere to bring together, to add; con- + tribuere to
   grant, impart. See Tribute.]
   To give or grant i common with others; to give to a common
   stock or for a common purpose; to furnish or suply in part;
   to give (money or other aid) for a specified object; as, to
   contribute food or fuel for the poor.
   [1913 Webster]

         England contributes much more than any other of the
         allies.                                  --Addison.
   [1913 Webster]

WordNet (r) 3.0 (2006):

contributing
    adj 1: tending to bring about; being partly responsible for;
           "working conditions are not conducive to productivity";
           "the seaport was a contributing factor in the growth of
           the city"; "a contributory factor" [syn: conducive,
           contributing(a), contributive, contributory,
           tributary]