tributary in WordNet English dictionary

1. a branch that flows into the main stream
   feeder  tributary  confluent  affluent 
   

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"
   conducive  contributing  contributive  contributory  tributary 
   
2. paying tribute
   "a tributary colony"
   tributary 
   
3. (of a stream) flowing into a larger stream
   tributary